Genetically modified mouse whose genome comprises a humanized CD274 gene

ABSTRACT

Non-human animals, methods and compositions for making and using the same, are provided, wherein said non-human animals comprise a humanization of a Cluster of Differentiation 274 (CD274) gene. Such non-human animals may be described, in some embodiments, as having a genetic modification to an endogenous CD274 gene so that said non-human animals express a Programmed cell death ligand 1 (PD-L1) polypeptide that includes a human portion and an endogenous portion (e.g., a non-human portion).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/963,402, filed Dec. 9, 2015, which claims the benefit of U.S.Provisional Application No. 62/106,525, filed Jan. 22, 2015 and U.S.Provisional Application No. 62/089,549, filed Dec. 9, 2014, the entirecontents of which are incorporated herein by reference.

INCORPORATION BY REFERENCE OF SEQUENCE LISTING

The Sequence Listing in the ASCII text file, named as31971Z_10133US02_SequenceListing.txt of 79 KB, created on Jan. 30, 2018,and submitted to the United States Patent and Trademark Office viaEFS-Web, is incorporated herein by reference.

BACKGROUND

Despite significant advancements in the treatment of autoimmunity,cancer and infectious diseases, major challenges in the globalhealthcare industry remain. These major challenges are due, in part, tothe ability of cells to modulate the immune response via cell surfacepolypeptides. Through some cell surface polypeptides cells andmicroorganisms have usurped signaling pathways to attenuate themonitoring mechanisms of the host immune system and inhibit immuneresponses to them, which leads to the development of disease phenotypes.Still, development of in vivo systems to optimally determine thetherapeutic potential of new targeted therapies for autoimmunity, cancerand infectious diseases that are designed to modulate the immuneresponses to such disease pathologies and determine the molecularaspects of how such cells manipulate immune responses is lacking. Suchin vivo systems provide a source for assays for assessing thetherapeutic efficacy and development of candidate agents for thetreatment of autoimmunity, cancer and infectious diseases in the future.

SUMMARY

The present invention encompasses the recognition that it is desirableto engineer non-human animals to permit improved in vivo systems foridentifying and developing new therapeutics and, in some embodiments,therapeutic regimens, which can be used for the treatment ofautoimmunity, inflammatory diseases and cancer. The present inventionalso encompasses the recognition that it is desirable to engineernon-human animals to permit improved in vivo systems for identifying anddeveloping new therapeutics and, in some embodiments, therapeuticregimens, which can be used for the treatment of infectious diseases.Further, the present invention also encompasses the recognition thatnon-human animals having a humanized CD274 gene and/or otherwiseexpressing, containing, or producing a human or humanized PD-L1polypeptide are desirable, for example for use in identifying anddeveloping therapeutics that up-regulate anti-tumor and/oranti-microbial immunity. In some embodiments, non-human animals of thepresent invention provide improved in vivo systems for theidentification and development of combination therapies that includetargeting PD-L1 or indirectly targeting a PD-L1 binding partner (e.g.,PD-1, B7-1).

In some embodiments, the present invention provides a non-human animalhaving a genome comprising a CD274 gene that includes genetic materialfrom two different species (e.g., a human and a non-human). In someembodiments, the CD274 gene of a non-human animal as described hereinencodes a PD-L1 polypeptide that contains human and non-human portions,wherein the human and non-human portions are linked together and form afunctional PD-L1 polypeptide. In some embodiments, a non-human portionincludes an endogenous portion. In some embodiments, a CD274 gene of anon-human animal as described herein encodes a PD-L1 polypeptide thatcontains an extracellular domain, in whole or in part, of a human PD-L1polypeptide.

In some embodiments, the present invention provides a non-human animalthat expresses a PD-L1 polypeptide, which PD-L1 polypeptide comprises ahuman portion and an endogenous portion. In some embodiments, a PD-L1polypeptide of the present invention is translated in a cell of thenon-human animal with a non-human signal peptide; in some certainembodiments, a rodent signal peptide.

In some embodiments, an endogenous portion comprises an intracellularportion of an endogenous PD-L1 polypeptide. In some embodiments, anendogenous portion further comprises a transmembrane portion of anendogenous PD-L1 polypeptide. In some embodiments, an endogenous portionhas an amino acid sequence that is at least 50%, at least 60%, at least70%, at least 80%, at least 90%, at least 95%, or at least 98% identicalto a corresponding amino acid sequence of a mouse PD-L1 polypeptide thatappears in FIG. 6. In some embodiments, an endogenous portion has anamino acid sequence that is substantially identical to a correspondingamino acid sequence of a mouse PD-L1 polypeptide that appears in FIG. 6.In some embodiments, an endogenous portion has an amino acid sequencethat is identical to a corresponding amino acid sequence of a mousePD-L1 polypeptide that appears in FIG. 6.

In some embodiments, a human portion comprises amino acids 19-238 of ahuman PD-L1 polypeptide. In some embodiments, a human portion comprisesamino acids 19-277 of a human PD-L1 polypeptide. In some embodiments, ahuman portion comprises amino acids 19-131 of a human PD-L1 polypeptide.In some embodiments, a human portion comprises an amino acid sequencethat is at least 50%, at least 60%, at least 70%, at least 80%, at least90%, at least 95%, or at least 98% identical to a corresponding aminoacid sequence of a human PD-L1 polypeptide that appears in FIG. 6. Insome embodiments, a human portion comprises an amino acid sequence thatis substantially identical to a corresponding amino acid sequence of ahuman PD-L1 polypeptide that appears in FIG. 6. In some embodiments, ahuman portion comprises an amino acid sequence that is identical to acorresponding amino acid sequence of a human PD-L1 polypeptide thatappears in FIG. 6.

In some embodiments, a PD-L1 polypeptide of the present invention isencoded by a CD274 gene that includes an endogenous non-human CD274sequence and a human CD274 sequence. In some certain embodiments, aCD274 gene comprises endogenous CD274 exons 1, 2, 6 and 7. In somecertain embodiments, a CD274 gene further comprises an endogenous CD274exon 5 in whole or in part. In some embodiments a CD274 gene thatincludes an endogenous non-human CD274 sequence and a human CD274sequence is located at an endogenous CD274 locus.

In some embodiments, a CD274 gene of the present invention comprises asequence that is at least 50%, at least 60%, at least 70%, at least 80%,at least 90%, at least 95%, or at least 98% identical to SEQ ID NO:12,SEQ ID NO:13 or SEQ ID NO:16. In some embodiments, a CD274 gene of thepresent invention comprises a sequence that is substantially identicalto SEQ ID NO:12, SEQ ID NO:13 or SEQ ID NO:16. In some embodiments, aCD274 gene of the present invention comprises a sequence that isidentical to SEQ ID NO:12, SEQ ID NO:13 or SEQ ID NO:16.

In some embodiments, a CD274 gene of the present invention comprises SEQID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15 and SEQ ID NO: 16. In someembodiments, a CD274 gene of the present invention comprises SEQ ID NO:13 and SEQ ID NO: 16. In some embodiments, a CD274 gene of the presentinvention comprises SEQ ID NO: 12 and SEQ ID NO: 13. In someembodiments, a CD274 gene of the present invention comprises SEQ ID NO:12, SEQ ID NO: 13 and SEQ ID NO: 17. In some embodiments, a CD274 geneof the present invention comprises SEQ ID NO: 13, SEQ ID NO: 16 and SEQID NO: 17.

In some embodiments, the present invention provides a humanized CD274locus. In some embodiments, a humanized CD274 locus is an endogenousnon-human CD274 locus that has been genetically modified to include ahuman CD274 sequence. In some embodiments, the present inventionprovides a humanized CD274 locus comprising one or more exons of anon-human CD274 gene operably linked to one or more exons, in whole orin part, of a human CD274 gene. In some embodiments, a humanized CD274locus further comprises 5′ and 3′ non-human CD274 untranslated regions(UTRs) flanking the one or more exons of a human CD274 gene. In someembodiments, a humanized CD274 locus is under the control of a rodentpromoter; in some certain embodiments, an endogenous rodent promoter.

In some embodiments, a humanized CD274 locus comprises non-human CD274exons 1, 2, 6 and 7 operably linked to human CD274 exons 3 and 4. Insome embodiments, a humanized CD274 locus comprises non-human CD274exons 1, 2, 6 and 7, human CD274 exons 3 and 4, and further comprises aCD274 exon 5, which CD274 exon 5 comprises a human portion and anon-human portion, and wherein said non-human and human exons areoperably linked. In some embodiments, a human portion of a CD274 exon 5includes nucleotides that encode amino acid residues that are a part ofthe extracellular domain of a human PD-L1 polypeptide. In someembodiments, a human portion of a CD274 exon 5 includes nucleotides thatencode amino acid residues 229-238 of a human PD-L1 polypeptide. In someembodiments, a human portion of a CD274 exon 5 includes about 32 bp of ahuman CD274 exon 5. In some embodiments, a non-human portion of a CD274exon 5 includes nucleotides that encode a transmembrane sequence. Insome embodiments, a non-human portion of a CD274 exon 5 includes about69 bp of a rodent CD274 exon 5. In some certain embodiments, a humanizedCD274 locus comprises a CD274 exon 5 having a sequence set forth in SEQID NO: 12. In some certain embodiments, a humanized CD274 locuscomprises a CD274 exon 5 that encodes amino acids corresponding toL229-R238 of a human PD-L1 polypeptide and amino acids corresponding toT238-Q263 of a rodent PD-L1 polypeptide.

In some embodiments, the present invention provides a non-human animalcomprising a CD274 gene that comprises an endogenous portion and a humanportion, wherein the endogenous and human portions are operably linkedto a non-human CD274 promoter. In some embodiments, a non-human CD274promoter is a rodent CD274 promoter. In some certain embodiments, arodent CD274 promoter is an endogenous rodent CD274 promoter.

In some embodiments, an endogenous portion comprises endogenous CD274exons 1, 2, 6 and 7. In some embodiments, an endogenous portion furthercomprises an endogenous CD274 exon 5 in whole or in part. In someembodiments, endogenous CD274 exons 1, 2, 5 in whole or in part, 6 and 7of the endogenous CD274 gene are at least 50%, at least 60%, at least70%, at least 80%, at least 90%, at least 95%, or at least 98% identicalto the corresponding exons 1, 2, 5 in whole or in part, 6 and 7 of amouse Cd274 gene that appears in FIG. 6. In some embodiments, endogenousCD274 exons 1, 2, 5 in whole or in part, 6 and 7 of the endogenous CD274gene are substantially identical to the corresponding exons 1, 2, 5 inwhole or in part, 6 and 7 of a mouse Cd274 gene that appears in FIG. 6.In some embodiments, endogenous CD274 exons 1, 2, 5 in whole or in part,6 and 7 of the endogenous CD274 gene are identical to the correspondingexons 1, 2, 5 in whole or in part, 6 and 7 of a mouse Cd274 gene thatappears in FIG. 6.

In some embodiments, a human portion encodes amino acids 19-131, 19-227or 19-238 of a human PD-L1 polypeptide.

In some embodiments, a human portion comprises exons 3 and 4 of a humanCD274 gene. In some embodiments, a human portion further comprises ahuman CD274 exon 5 in whole or in part. In some embodiments, human CD274exons 3, 4, and 5 in whole or in part, are at least 50%, at least 60%,at least 70%, at least 80%, at least 900, at least 95%, or at least 98%identical to the corresponding exons 3, 4 and 5, in whole or in part, ofa human CD274 gene that appears in FIG. 6. In some embodiments, humanCD274 exons 3, 4, and 5 in whole or in part, are substantially identicalto the corresponding exons 3, 4, and 5 in whole or in part, of a humanCD274 gene that appears in FIG. 6. In some embodiments, human CD274exons 3, 4, and 5 in whole or in part, are identical to thecorresponding exons 3, 4, and 5 in whole or in part, of a human CD274gene that appears in FIG. 6. In some embodiments, a human portioncomprises a sequence that is codon-optimized for expression in anon-human animal; in some embodiments, expression in a rodent; in somecertain embodiments, expression in a mouse or rat.

In some embodiments, a human portion includes a sequence that is atleast 50%, at least 60%, at least 70%, at least 80%, at least 90%, or atleast 95% identical to SEQ ID NO: 9, SEQ ID NO:10, SEQ ID NO:11 or SEQID NO:12. In some embodiments, a human portion includes a sequence thatis substantially identical to SEQ ID NO: 9, SEQ ID NO:10, SEQ ID NO: 11or SEQ ID NO: 12. In some embodiments, a human portion includes asequence that is identical to SEQ ID NO: 9, SEQ ID NO:10, SEQ ID NO: 11or SEQ ID NO: 12. In some embodiments, a human portion comprises SEQ IDNO: 9, SEQ ID NO: 10, SEQ ID NO:11 or SEQ ID NO:12. In some embodiments,a human portion comprises a sequence that is identical to orsubstantially identical to SEQ ID NO: 7, SEQ ID NO:8 or SEQ ID NO: 11.In some embodiments, a human portion comprises SEQ ID NO: 7, SEQ ID NO:8or SEQ ID NO:11.

In some embodiments, a non-human animal of the present invention has agenome comprising a CD274 gene that comprises SEQ ID NO:8, SEQ ID NO:9,SEQ ID NO:10, SEQ ID NO: 11, SEQ ID NO:12, SEQ ID NO:13, SEQ ID NO:16,SEQ ID NO:17 or a combination thereof.

In some embodiments, the present invention provides a PD-L1 polypeptideproduced, expressed, or generated from a non-human animal as describedherein. In some certain embodiments, a PD-L1 polypeptide produced,expressed, or generated from a non-human animal as described hereincomprises an amino acid sequence that is at least 50%, at least 60%, atleast 70%, at least 80%, at least 90%, at least 95%, or at least 98%identical to a humanized PD-L1 polypeptide that appears in FIG. 6. Insome certain embodiments, a PD-L1 polypeptide produced, expressed, orgenerated from a non-human animal as described herein comprises an aminoacid sequence that is substantially identical to a humanized PD-L1polypeptide that appears in FIG. 6. In some certain embodiments, a PD-L1polypeptide produced, expressed, or generated from a non-human animal asdescribed herein comprises an amino acid sequence that is identical to ahumanized PD-L polypeptide that appears in FIG. 6.

In some embodiments, the present invention provides an isolated cell ortissue from a non-human animal as described herein. In some embodiments,an isolated cell or tissue comprises a CD274 gene as described herein.In some embodiments, a cell is from a lymphoid lineage. In someembodiments, a cell is from a myeloid lineage. In some embodiments, acell is selected from a B cell, dendritic cell, macrophage, monocyte,and a T cell. In some embodiments, a tissue is selected from adipose,bladder, brain, breast, bone marrow, eye, heart, intestine, kidney,liver, lung, lymph node, muscle, pancreas, plasma, serum, skin, spleen,stomach, thymus, testis, ovum, and a combination thereof.

In some embodiments, the present invention provides a non-humanembryonic stem cell whose genome comprises a CD274 gene as describedherein. In some embodiments, a non-human embryonic stem cell is a rodentembryonic stem cell. In some certain embodiments, a rodent embryonicstem cell is a mouse embryonic stem cell and is from a 129 strain, C57BLstrain, or a mixture thereof. In some certain embodiments, a rodentembryonic stem cell is a mouse embryonic stem cell and is a mixture of129 and C57BL strains.

In some embodiments, a non-human embryonic stem cell of the presentinvention has a genome comprising a CD274 gene that comprises SEQ ID NO:13, SEQ ID NO:14, SEQ ID NO: 15, SEQ ID NO: 16 or a combination thereof.

In some embodiments, the present invention provides the use of anon-human embryonic stem cell as described herein to make a non-humananimal. In some certain embodiments, a non-human embryonic stem cell isa mouse embryonic stem cell and is used to make a mouse comprising aCD274 gene as described herein. In some certain embodiments, a non-humanembryonic stem cell is a rat embryonic stem cell and is used to make arat comprising a CD274 gene as described herein.

In some embodiments, the present invention provides a non-human embryocomprising, made from, obtained from, or generated from a non-humanembryonic stem cell comprising a CD274 gene as described herein. In somecertain embodiments, a non-human embryo is a rodent embryo; in someembodiments, a mouse embryo; in some embodiments, a rat embryo.

In some embodiments, the present invention provides the use of anon-human embryo as described herein to make a non-human animal. In somecertain embodiments, a non-human embryo is a mouse embryo and is used tomake a mouse comprising a CD274 gene as described herein. In somecertain embodiments, a non-human embryo is a rat embryo and is used tomake a rat comprising a CD274 gene as described herein.

In some embodiments, the present invention provides a targeting vectoror nucleic acid construct as described herein. In some embodiments, thepresent invention provides a targeting vector or nucleic acid constructthat comprises a humanized CD274 gene as described herein. In someembodiments, the present invention provides a targeting vector (ornucleic acid construct) that comprises a CD274 gene that encodes a PD-L1polypeptide that comprises a human extracellular domain in whole or inpart; in some certain embodiments a PD-L1 polypeptide that comprisesamino acids 19-131, 19-227 or 19-238 of a human PD-L1 polypeptide.

In some embodiments, a targeting vector or nucleic acid construct of thepresent invention comprises one or more exons, in whole or in part, of anon-human CD274 gene operably linked to one or more exons, in whole orin part, of a human CD274 gene. In some embodiments, a targeting vectoror nucleic acid construct comprises 5′ and 3′ non-human CD274untranslated regions (UTRs) flanking the one or more exons of a humanCD274 gene. In some embodiments, a targeting vector or nucleic acidconstruct comprises one or more selection markers. In some embodiments,a targeting vector or nucleic acid construct comprises one or moresite-specific recombination sites. In some embodiments, a targetingvector or nucleic acid construct comprises human CD274 exons 3 and 4. Insome embodiments, a targeting vector or nucleic acid construct compriseshuman CD274 exons 3 and 4 and a human CD274 exon 5 in whole or in part.

In some embodiments, a targeting vector or nucleic acid constructcomprises SEQ ID NO:7. In some certain embodiments, a targeting vectoror nucleic acid construct comprises a sequence that is identical orsubstantially identical to any one of SEQ ID NO:9, SEQ ID NO:10 and SEQID NO: 11.

In some embodiments, the present invention provides use of a targetingvector or nucleic acid construct as described herein to make a modifiednon-human embryonic stem cell. In some embodiments, the presentinvention provides use of a targeting vector or nucleic acid constructas described herein to make a modified non-human cell. In someembodiments, the present invention provides use of a targeting vector ornucleic acid construct as described herein to make a modified non-humanembryo. In some embodiments, the present invention provides use of atargeting vector or nucleic acid construct as described herein to make anon-human animal.

In some embodiments, the present invention provides a method of making anon-human animal that expresses a PD-L1 polypeptide from an endogenousCD274 gene, wherein the PD-L1 polypeptide comprises a human sequence,the method comprising (a) inserting a genomic fragment into anendogenous CD274 gene in a non-human embryonic stem cell, said genomicfragment comprising a nucleotide sequence that encodes a human PD-L1polypeptide in whole or in part; (b) obtaining the non-human embryonicstem cell generated in (a); and, (c) creating a non-human animal usingthe rodent embryonic stem cell of (b).

In some embodiments, a human sequence comprises amino acids 19-131,19-227 or 19-238 of a human PD-L1 polypeptide.

In some embodiments, a nucleotide sequence comprises human CD274 exons 3and 4. In some embodiments, a nucleotide sequence further compriseshuman CD274 exon 5 in whole or in part. In some embodiments, anucleotide sequence comprises one or more selection markers. In someembodiments, a nucleotide sequence comprises one or more site-specificrecombination sites.

In some embodiments, the present invention provides a method of making anon-human animal whose genome comprises a CD274 gene that encodes aPD-L1 polypeptide having a human portion and an endogenous portion,which portions are operably linked to a non-human CD274 promoter, themethod comprising modifying the genome of a non-human animal so that itcomprises a CD274 gene that encodes a PD-L1 polypeptide having a humanportion and an endogenous portion, which portions are operably linked toa non-human CD274 promoter, thereby making said non-human animal. Insome embodiments, a non-human CD274 promoter is a rodent CD274 promoter.In some certain embodiments, a rodent CD274 promoter is an endogenousrodent CD274 promoter.

In some embodiments, a human portion comprises amino acids 19-131,19-227 or 19-238 of a human PD-L1 polypeptide.

In some embodiments, a CD274 gene is modified to include human CD274exons 3 and 4. In some embodiments, a CD274 gene is modified to includehuman CD274 exons 3, 4, and 5 in whole or in part.

In some embodiments, modifying the genome of a non-human animal isperformed in a non-human embryonic stem cell followed by generating anon-human animal with said non-human embryonic stem cell. In somecertain embodiments, the non-human embryonic stem cell is a rodentembryonic stem cell; in some embodiments, a mouse embryonic stem cell;in some embodiments, a rat embryonic stem cell.

In some embodiments, the present invention provides a non-human animalobtainable by, generated from, or produced from a method as describedherein.

In some embodiments, the present invention provides a method ofreducing, preventing or eliminating tumor growth in a non-human animal,the method comprising the steps of administering a drug targeting humanPD-L1 to a non-human animal whose genome comprises a CD274 gene thatencodes a PD-L1 polypeptide having a human portion and an endogenousportion, which portions are operably linked to a non-human animal CD274promoter; the administering being performed under conditions and for atime sufficient that tumor growth is reduced, prevented or eliminated inthe non-human animal.

In some embodiments, the present invention provides a method of killingtumor cells in a non-human animal, the method comprising the steps ofadministering a drug targeting human PD-L1 to a non-human animal whosegenome comprises a CD274 gene that encodes a PD-L1 polypeptide having ahuman portion and an endogenous portion, which portions are operablylinked to a non-human animal CD274 promoter; the administering beingperformed under conditions and for a time sufficient that the drugmediates killing of the tumor cells in the non-human animal.

In some embodiments, the present invention provides a method ofassessing the pharmacokinetic properties of a drug targeting humanPD-L1, the method comprising the steps of administering a drug targetinghuman PD-L1 to a non-human animal whose genome comprises a CD274 genethat encodes a PD-L1 polypeptide having a human portion and anendogenous portion, which portions are operably linked to a non-humananimal CD274 promoter; and performing an assay to determine one or morepharmacokinetic properties of the drug targeting human PD-L1.

In some embodiments, the present invention provides a method ofassessing the efficacy of a drug targeting human PD-L1, the methodcomprising the steps of administering a drug targeting human PD-L1 to anon-human animal whose genome comprises a CD274 gene that encodes aPD-L1 polypeptide having a human portion and an endogenous portion,which portions are operably linked to a non-human animal CD274 promoter;and performing an assay to determine the efficacy of the drug targetinghuman PD-L1.

In various embodiments, a non-human animal as described herein is arodent whose genome includes a CD274 gene that encodes a PD-L1polypeptide having a human portion and an endogenous portion, whichportions are operably linked to a rodent CD274 promoter. In variousembodiments, a rodent CD274 promoter is an endogenous rodent CD274promoter. In various embodiments, a human portion comprises amino acids19-131, 19-227 or 19-238 of a human PD-L1 polypeptide.

In some embodiments, a drug targeting human PD-L1 is a PD-L1 antagonist.In some embodiments, a drug targeting human PD-L1 is a PD-L1 agonist. Insome embodiments, a drug targeting human PD-L1 is an anti-PD-L1antibody. In some embodiments, a drug targeting human PD-L1 isadministered to a non-human animal intravenously, intraperitoneally,intramuscularly, or subcutaneously.

In some embodiments, the present invention provides a method foridentification or validation of a drug or vaccine, the method comprisingthe steps of delivering a drug or vaccine to a non-human animal whosegenome includes a CD274 gene as described herein, and monitoring one ormore of the immune response to the drug or vaccine, the safety profileof the drug or vaccine, or the effect on a disease, disorder orcondition. In some embodiments, monitoring the safety profile includesdetermining if the non-human animal exhibits a side effect or adversereaction as a result of delivering the drug or vaccine. In someembodiments, a side effect or adverse reaction is selected frommorbidity, mortality, alteration in body weight, alteration of the levelof one or more enzymes (e.g., liver), alteration in the weight of one ormore organs, loss of function (e.g., sensory, motor, organ, etc.),increased susceptibility to one or more diseases, alterations to thegenome of the non-human animal, increase or decrease in food consumptionand complications of one or more diseases. In some embodiments, thedisease, disorder or condition is induced in the non-human animal. Insome embodiments, the disease, disorder or condition induced in thenon-human animal is associated with a disease, disorder or conditionsuffered by one or more human patients in need of treatment. In somecertain embodiments, the drug is an antibody.

In some embodiments, the present invention provides use of a non-humananimal as described herein in the development of a drug or vaccine foruse in medicine, such as use as a medicament.

In some embodiments, the present invention provides use of a non-humananimal as described herein in the manufacture of a medicament for thetreatment of cancer or a neoplasm.

In some embodiments, the present invention provides use of a non-humananimal as described herein in the manufacture of a medicament of thetreatment of an infectious disease.

In some embodiments, the present invention provides use of a non-humananimal as described herein in the manufacture of a medicament of thetreatment of an inflammatory disease, disorder or condition.

In some embodiments, the present invention provides use of a non-humananimal as described herein in the manufacture of a medicament of thetreatment of an autoimmune disease, disorder or condition.

In various embodiments, a CD274 gene of the present invention includes aCD274 gene as described herein. In various embodiments, a CD274 gene ofthe present invention encodes a PD-L1 polypeptide having a human portionand an endogenous portion, which portions are operably linked to arodent CD274 promoter. In various embodiments, a rodent promoter is anendogenous rodent promoter. In various embodiments, a human portioncomprises human CD274 exons 3 and 4. In various embodiments, a humanportion comprises human CD274 exons 3 and 4 and a human CD274 exon 5 inwhole or in part.

In various embodiments, a PD-L1 polypeptide of the present inventionincludes a PD-L1 polypeptide as described herein.

In various embodiments, a non-human animal of the present invention doesnot detectably express a full-length endogenous non-human PD-L1polypeptide. In various embodiments, a non-human animal of the presentinvention does not detectably express an extracellular portion of anendogenous PD-L1 polypeptide. In various embodiments, a non-human animalof the present invention does not detectably express an immunoglobulin Vdomain and, in some embodiments, an immunoglobulin C domain of anendogenous PD-L1 polypeptide.

In various embodiments, a non-human animal of the present invention is arodent; in some embodiments, a mouse; in some embodiments, a rat.

As used in this application, the terms “about” and “approximately” areused as equivalents. Any numerals used in this application with orwithout about/approximately are meant to cover any normal fluctuationsappreciated by one of ordinary skill in the relevant art.

Other features, objects, and advantages of the present invention areapparent in the detailed description of certain embodiments thatfollows. It should be understood, however, that the detaileddescription, while indicating certain embodiments of the presentinvention, is given by way of illustration only, not limitation. Variouschanges and modifications within the scope of the invention will becomeapparent to those skilled in the art from the detailed description.

BRIEF DESCRIPTION OF THE DRAWING

The Drawing included herein, which is composed of the following Figures,is for illustration purposes only and not for limitation.

FIG. 1 shows a diagram, not to scale, of the genomic organization of anon-human (e.g., mouse) and human cluster of differentiation 274 (CD274)genes. Exons are numbered beneath each exon. Untranslated regions (UTRs)are indicated by open rectangles.

FIG. 2 shows an illustration, not to scale, of an exemplary constructsused in humanization of a non-human cluster of differentiation 274(CD274) gene. Top diagram represents a humanized targeting vector with aneomycin cassette, while the bottom diagram represents a humanizedtargeting vector with the cassette deleted. Selected nucleotide junctionlocations are marked with a line below each junction accompanied by thecorresponding SEQ ID NOs. Exemplary humanization fragments are set forthin FIG. 6 and are illustrated as follows: humanization fragment A: human4,494 bp-neomycin cassette-human 3,950 bp (SEQ ID NO:7); humanizationfragment B: human 4,494 bp-loxP-human 3,950 bp (SEQ ID NO:8);humanization fragment C: human 4,494 bp fragment (SEQ ID NO:9);humanization fragment D: human 3,950 bp fragment (SEQ ID NO: 10).

FIG. 3 shows a diagram, not to scale, of the genomic organization of anon-human (e.g., mouse) and human cluster of differentiation 274 (CD274)genes indicating the approximate locations of probes used in an assaydescribed in Example 1. Also illustrated are an exemplary humanizationfragment (humanization fragment E; SEQ ID NO: 11) within a human CD274gene and an exemplary deletion of a portion of a mouse Cd274 gene.

FIG. 4 shows exemplary MC38.ova/hPD-L1 tumor growth curves over 21 daysin mice homozygous for humanization of an endogenous PD-L1 gene asdescribed in Example 1. Control Ab: antibody not specific for PD-L1,a-hPD-L1: antibody specific for human PD-L1. Arrows indicate the daysfor antibody treatment during the experiment. The number of tumor-freemice on day 21 is shown for each treatment group.

FIG. 5 shows exemplary real-time PCR analysis of CD8b, CD3 and PD-L1mRNA expression in splenocytes of mice homozygous for an endogenousCD274 gene as described in Example 1 after treatment with anti-PD-L1 orcontrol antibodies. A, mean of six mice per group. B, expression levelsfor individual mice in each treatment group. Control Ab: antibody notspecific for PD-L1; a-PD-L: anti-PD-L1 antibody.

FIG. 6 shows exemplary mouse, human and humanized CD274 and PD-L1sequences, as well as exemplary human nucleic acid sequences forhumanization of a non-human CD274 gene. For mRNA sequences, bold fontindicates coding sequence and consecutive exons, where indicated, areseparated by alternating underlined text; for humanized mRNA sequences,human sequences are contained within parentheses. For protein sequences,signal peptides are underlined, extracellular sequences are bold font,immunoglobulin V (IgV) domain sequences are within parentheses, andintracellular sequences are italicized; for humanized protein sequences,non-human sequences are indicated in regular font, human sequences areindicated in bold font. Humanization fragment A: human 4,494 bp-neomycincassette-human 3,950 bp (SEQ ID NO:7); humanization fragment B: human4,494 bp-loxP-human 3,950 bp (SEQ ID NO:8); humanization fragment C:human 4,494 bp fragment (SEQ ID NO:9); humanization fragment D: human3,950 bp fragment (SEQ ID NO:10).

DEFINITIONS

This invention is not limited to particular methods and experimentalconditions described herein, as such methods and conditions may vary. Itis also to be understood that the terminology used herein is for thepurpose of describing particular embodiments only, and is not intendedto be limiting, since the scope of the present invention is defined bythe claims.

Unless defined otherwise, all terms and phrases used herein include themeanings that the terms and phrases have attained in the art, unless thecontrary is clearly indicated or clearly apparent from the context inwhich the term or phrase is used. Although any methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, particular methods andmaterials are now described. All publications mentioned herein arehereby incorporated by reference.

The term “approximately”, as applied herein to one or more values ofinterest, includes a value that is similar to a stated reference value.In certain embodiments, the term “approximately” or “about” refers to arange of values that fall within 25%, 20%, 19%, 18%, 17%, 16%, 15%, 14%,13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or less ineither direction (greater than or less than) of the stated referencevalue unless otherwise stated or otherwise evident from the context(except where such number would exceed 100% of a possible value).

The term “biologically active”, as used herein, includes acharacteristic of any agent that has activity in a biological system, invitro or in vivo (e.g., in an organism). For instance, an agent that,when present in an organism, has a biological effect within thatorganism is considered to be biologically active. In particularembodiments, where a protein or polypeptide is biologically active, aportion of that protein or polypeptide that shares at least onebiological activity of the protein or polypeptide is typically referredto as a “biologically active” portion.

The phrase “cluster of differentiation 274 protein”, “CD274 protein”,“B7-H1 protein”, or “PD-L1 protein” as used herein, includes atransmembrane protein that belongs to the B7 family of cell-surfaceprotein ligands and has extracellular immunoglobulin V (IgV) andimmunoglobulin constant-like (IgC) domains, which are related toimmunoglobulin variable and constant domains, and transmembrane andcytoplasmic (or intracellular) domains. PD-L1 is expressed in bothlymphoid (e.g., B cell, T cell, dendritic cell, macrophages, monocytes,etc.) and non-lymphoid lineages (heart, lung, liver, pancreas, etc.) andis involved in interactions between membrane surface proteins such as,for example, Programmed cell death 1 (PD-1) to regulate immune function.Expression of PD-L1 is regulated by cytokines (e.g., interferon-γ) andhas been reported to be up-regulated in many human cancers, which mayallow such cancers to evade surveillance by the immune system. PD-L1 hasbeen shown to be involved in several cellular processes such as, forexample, intracellular infection, peripheral tolerance, T cell receptorsignaling and T cell proliferation. Alternatively spliced CD274 isoformshave been identified between mouse and man. By way of illustration,nucleotide and amino acid sequences of murine and human CD274 genes areprovided in FIG. 6. Persons of skill upon reading this disclosure willrecognize that one or more endogenous CD274 genes in a genome (or all)can be replaced, modified, altered, deleted, disrupted, etc. by one ormore heterologous CD274 genes (e.g., polymorphic variants, subtypes ormutants, genes from another species, humanized forms, etc.).

A “CD274-expressing cell”, “B7-H1-expressing cell”, or “PD-L1-expressingcell” as used herein, includes a cell that expresses a PD-L1transmembrane polypeptide. In some embodiments, a PD-L1-expressing cellexpresses PD-L1 transmembrane polypeptides on its surface. In someembodiments, PD-L1 polypeptides are expressed on the surface of the cellin an amount sufficient to mediate cell-to-cell interactions (e.g.,through interactions with PD-1 receptor polypeptides). ExemplaryPD-L-expressing cells include B cells, dendritic cells, macrophages,monocytes and T cells. PD-L1-expressing cells modulate activation orinhibition of lymphoid cells to augment or attenuate immune responses.In some embodiments, non-human animals of the present inventiondemonstrate regulation of various cellular processes (as describedherein) via humanized PD-L1 polypeptides expressed on the surface of onemore cells of the non-human animal.

The term “comparable”, as used herein, includes two or more agents,entities, situations, sets of conditions, etc. that may not be identicalto one another but that are sufficiently similar to permit comparisonbetween them so that conclusions may reasonably be drawn based ondifferences or similarities observed. Those of ordinary skill in the artwill understand, in context, what degree of identity is required in anygiven circumstance for two or more such agents, entities, situations,sets of conditions, etc. to be considered comparable.

The term “conservative”, as used herein to describe a conservative aminoacid substitution, includes substitution of an amino acid residue byanother amino acid residue having a side chain R group with similarchemical properties (e.g., charge or hydrophobicity). In general, aconservative amino acid substitution will not substantially change thefunctional properties of interest of a protein, for example, the abilityof a receptor to bind to a ligand. Examples of groups of amino acidsthat have side chains with similar chemical properties include:aliphatic side chains such as glycine, alanine, valine, leucine, andisoleucine; aliphatic-hydroxyl side chains such as serine and threonine;amide-containing side chains such as asparagine and glutamine; aromaticside chains such as phenylalanine, tyrosine, and tryptophan; basic sidechains such as lysine, arginine, and histidine; acidic side chains suchas aspartic acid and glutamic acid; and, sulfur-containing side chainssuch as cysteine and methionine. Conservative amino acids substitutiongroups include, for example, valine/leucine/isoleucine,phenylalanine/tyrosine, lysine/arginine, alanine/valine,glutamate/aspartate, and asparagine/glutamine. In some embodiments, aconservative amino acid substitution can be a substitution of any nativeresidue in a protein with alanine, as used in, for example, alaninescanning mutagenesis. In some embodiments, a conservative substitutionis made that has a positive value in the PAM250 log-likelihood matrixdisclosed in Gonnet, G. H. et al., 1992, Science 256:1443-1445, herebyincorporated by reference. In some embodiments, a substitution is amoderately conservative substitution wherein the substitution has anonnegative value in the PAM250 log-likelihood matrix.

The term “control”, as used herein, includes the art-understood meaningof a “control” being a standard against which results are compared.Typically, controls are used to augment integrity in experiments byisolating variables in order to make a conclusion about such variables.In some embodiments, a control is a reaction or assay that is performedsimultaneously with a test reaction or assay to provide a comparator. Asused herein, a “control” may refer to a “control animal.” A “controlanimal” may have a modification as described herein, a modification thatis different as described herein, or no modification (i.e., a wild-typeanimal). In one experiment, a “test” (i.e., a variable being tested) isapplied. In a second experiment, the “control,” the variable beingtested is not applied. In some embodiments, a control is a historicalcontrol (i.e., of a test or assay performed previously, or an amount orresult that is previously known). In some embodiments, a control is orcomprises a printed or otherwise saved record. A control may be apositive control or a negative control.

The term “disruption”, as used herein, includes the result of ahomologous recombination event with a DNA molecule (e.g., with anendogenous homologous sequence such as a gene or gene locus). In someembodiments, a disruption may achieve or represent an insertion,deletion, substitution, replacement, missense mutation, or a frame-shiftof a DNA sequence(s), or any combination thereof. Insertions may includethe insertion of entire genes or fragments of genes, e.g., exons, whichmay be of an origin other than the endogenous sequence (e.g., aheterologous sequence). In some embodiments, a disruption may increaseexpression and/or activity of a gene or gene product (e.g., of a proteinencoded by a gene). In some embodiments, a disruption may decreaseexpression and/or activity of a gene or gene product. In someembodiments, a disruption may alter sequence of a gene or an encodedgene product (e.g., an encoded protein). In some embodiments, adisruption may truncate or fragment a gene or an encoded gene product(e.g., an encoded protein). In some embodiments, a disruption may extenda gene or an encoded gene product; in some such embodiments, adisruption may achieve assembly of a fusion protein. In someembodiments, a disruption may affect level but not activity of a gene orgene product. In some embodiments, a disruption may affect activity butnot level of a gene or gene product. In some embodiments, a disruptionmay have no significant effect on level of a gene or gene product. Insome embodiments, a disruption may have no significant effect onactivity of a gene or gene product. In some embodiments, a disruptionmay have no significant effect on either level or activity of a gene orgene product.

The terms “determining”, “measuring”, “evaluating”, “assessing”,“assaying” and “analyzing” are used interchangeably herein to refer toany form of measurement, and include determining if an element ispresent or not. These terms include both quantitative and/or qualitativedeterminations. Assaying may be relative or absolute. “Assaying for thepresence of” can be determining the amount of something present and/ordetermining whether or not it is present or absent.

The phrase “endogenous locus” or “endogenous gene”, as used herein,includes a genetic locus found in a parent or reference organism priorto introduction of a disruption, deletion, replacement, alteration, ormodification as described herein. In some embodiments, the endogenouslocus has a sequence found in nature. In some embodiments, theendogenous locus is a wild type locus. In some embodiments, thereference organism is a wild-type organism. In some embodiments, thereference organism is an engineered organism. In some embodiments, thereference organism is a laboratory-bred organism (whether wild-type orengineered).

The phrase “endogenous promoter” includes a promoter that is naturallyassociated, e.g., in a wild-type organism, with an endogenous gene.

The term “heterologous”, as used herein, includes an agent or entityfrom a different source. For example, when used in reference to apolypeptide, gene, or gene product present in a particular cell ororganism, the term clarifies that the relevant polypeptide, gene, orgene product: 1) was engineered by the hand of man; 2) was introducedinto the cell or organism (or a precursor thereof) through the hand ofman (e.g., via genetic engineering); and/or 3) is not naturally producedby or present in the relevant cell or organism (e.g., the relevant celltype or organism type).

The term “host cell”, as used herein, includes a cell into which aheterologous (e.g., exogenous) nucleic acid or protein has beenintroduced. Persons of skill upon reading this disclosure willunderstand that such terms refer not only to the particular subjectcell, but also is used to refer to the progeny of such a cell. Becausecertain modifications may occur in succeeding generations due to eithermutation or environmental influences, such progeny may not, in fact, beidentical to the parent cell, but are still included within the scope ofthe term “host cell” as used herein. In some embodiments, a host cell isor comprises a prokaryotic or eukaryotic cell. In general, a host cellis any cell that is suitable for receiving and/or producing aheterologous nucleic acid or protein, regardless of the Kingdom of lifeto which the cell is designated. Exemplary cells include those ofprokaryotes and eukaryotes (single-cell or multiple-cell), bacterialcells (e.g., strains of E. coli, Bacillus spp., Streptomyces spp.,etc.), mycobacteria cells, fungal cells, yeast cells (e.g., S.cerevisiae, S. pombe, P. pastoris, P. methanolica, etc.), plant cells,insect cells (e.g., SF-9, SF-21, baculovirus-infected insect cells,Trichoplusia ni, etc.), non-human animal cells, human cells, or cellfusions such as, for example, hybridomas or quadromas. In someembodiments, the cell is a human, monkey, ape, hamster, rat, or mousecell. In some embodiments, the cell is eukaryotic and is selected fromthe following cells: CHO (e.g., CHO K1, DXB-1 CHO, Veggie-CHO), COS(e.g., COS-7), retinal cell, Vero, CV1, kidney (e.g., HEK293, 293 EBNA,MSR 293, MDCK, HaK, BHK), HeLa, HepG2, W138, MRC 5, Colo205, HB 8065,HL-60, (e.g., BHK21), Jurkat, Daudi, A431 (epidermal), CV-1, U937, 3T3,L cell, C127 cell, SP2/0, NS-0, MMT 060562, Sertoli cell, BRL 3A cell,HT1080 cell, myeloma cell, tumor cell, and a cell line derived from anaforementioned cell. In some embodiments, the cell comprises one or moreviral genes, e.g., a retinal cell that expresses a viral gene (e.g., aPER.C6® cell). In some embodiments, a host cell is or comprises anisolated cell. In some embodiments, a host cell is part of a tissue. Insome embodiments, a host cell is part of an organism.

The term “humanized”, is used herein in accordance with itsart-understood meaning to refer to nucleic acids or proteins whosestructures (i.e., nucleotide or amino acid sequences) include portionsthat correspond substantially or identically with structures of aparticular gene or protein found in nature in a non-human animal, andalso include portions that differ from that found in the relevantparticular non-human gene or protein and instead correspond more closelywith comparable structures found in a corresponding human gene orprotein. In some embodiments, a “hunmanized” gene is one that encodes apolypeptide having substantially the amino acid sequence as that of ahuman polypeptide (e.g., a human protein or portion thereof—e.g.,characteristic portion thereof). To give but one example, in the case ofa membrane receptor, a “humanized” gene may encode a polypeptide havingan extracellular portion having an amino acid sequence as that of ahuman extracellular portion and the remaining sequence as that of anon-human (e.g., mouse) polypeptide. In some embodiments, a humanizedgene comprises at least a portion of a DNA sequence of a human gene. Insome embodiment, a humanized gene comprises an entire DNA sequence of ahuman gene. In some embodiments, a humanized protein comprises asequence having a portion that appears in a human protein. In someembodiments, a humanized protein comprises an entire sequence of a humanprotein and is expressed from an endogenous locus of a non-human animalthat corresponds to the homolog or ortholog of the human gene.

The term “identity”, as used herein in connection with a comparison ofsequences, includes identity as determined by a number of differentalgorithms known in the art that can be used to measure nucleotideand/or amino acid sequence identity. In some embodiments, identities asdescribed herein are determined using a ClustalW v. 1.83 (slow)alignment employing an open gap penalty of 10.0, an extend gap penaltyof 0.1, and using a Gonnet similarity matrix (MACVECTOR™ 10.0.2,MacVector Inc., 2008).

“Improve,” “increase,” “eliminate,” or “reduce,” as used herein orgrammatical equivalents thereof, indicate values that are relative to abaseline measurement, such as a measurement in the same individual (oranimal) prior to initiation of a treatment described herein, or ameasurement in a control individual (or animal) or multiple controlindividuals (or animals) in the absence of the treatment describedherein.

The term “isolated”, as used herein, includes a substance and/or entitythat has been (1) separated from at least some of the components withwhich it was associated when initially produced (whether in natureand/or in an experimental setting), and/or (2) designed, produced,prepared, and/or manufactured by the hand of man. Isolated substancesand/or entities may be separated from about 10%, about 20%, about 30%,about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, about91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%,about 98%, about 99%, or more than about 99% of the other componentswith which they were initially associated. In some embodiments, isolatedagents are about 80%, about 85%, about 90%, about 91%, about 92%, about93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99%,or more than about 99% pure. As used herein, a substance is “pure” if itis substantially free of other components. In some embodiments, as willbe understood by those skilled in the art, a substance may still beconsidered “isolated” or even “pure”, after having been combined withcertain other components such as, for example, one or more carriers orexcipients (e.g., buffer, solvent, water, etc.); in such embodiments,percent isolation or purity of the substance is calculated withoutincluding such carriers or excipients. To give but one example, in someembodiments, a biological polymer such as a polypeptide orpolynucleotide that occurs in nature is considered to be “isolated”when: a) by virtue of its origin or source of derivation is notassociated with some or all of the components that accompany it in itsnative state in nature; b) it is substantially free of otherpolypeptides or nucleic acids of the same species from the species thatproduces it in nature; or c) is expressed by or is otherwise inassociation with components from a cell or other expression system thatis not of the species that produces it in nature. Thus, for instance, insome embodiments, a polypeptide that is chemically synthesized or issynthesized in a cellular system different from that which produces itin nature is considered to be an “isolated” polypeptide. Alternativelyor additionally, in some embodiments, a polypeptide that has beensubjected to one or more purification techniques may be considered to bean “isolated” polypeptide to the extent that it has been separated fromother components: a) with which it is associated in nature; and/or b)with which it was associated when initially produced.

The phrase “non-human animal”, as used herein, includes any vertebrateorganism that is not a human. In some embodiments, a non-human animal isa cyclostome, a bony fish, a cartilaginous fish (e.g., a shark or aray), an amphibian, a reptile, a mammal, and a bird. In someembodiments, a non-human mammal is a primate, a goat, a sheep, a pig, adog, a cow, or a rodent. In some embodiments, a non-human animal is arodent such as a rat or a mouse.

The phrase “nucleic acid”, as used herein, in its broadest sense,includes any compound and/or substance that is or can be incorporatedinto an oligonucleotide chain. In some embodiments, a “nucleic acid” isa compound and/or substance that is or can be incorporated into anoligonucleotide chain via a phosphodiester linkage. As will be clearfrom context, in some embodiments, “nucleic acid” includes individualnucleic acid residues (e.g., nucleotides and/or nucleosides); in someembodiments, “nucleic acid” includes an oligonucleotide chain comprisingindividual nucleic acid residues. In some embodiments, a “nucleic acid”is or comprises RNA; in some embodiments, a “nucleic acid” is orcomprises DNA. In some embodiments, a “nucleic acid” is, comprises, orconsists of one or more natural nucleic acid residues. In someembodiments, a “nucleic acid” is, comprises, or consists of one or morenucleic acid analogs. In some embodiments, a nucleic acid analog differsfrom a “nucleic acid” in that it does not utilize a phosphodiesterbackbone. For example, in some embodiments, a “nucleic acid” is,comprises, or consists of one or more “peptide nucleic acids”, which areknown in the art and have peptide bonds instead of phosphodiester bondsin the backbone, are considered within the scope of the presentinvention. Alternatively or additionally, in some embodiments, a“nucleic acid” has one or more phosphorothioate and/or5′-N-phosphoramidite linkages rather than phosphodiester bonds. In someembodiments, a “nucleic acid” is, comprises, or consists of one or morenatural nucleosides (e.g., adenosine, thymidine, guanosine, cytidine,uridine, deoxyadenosine, deoxythymidine, deoxyguanosine, anddeoxycytidine). In some embodiments, a “nucleic acid” is, comprises, orconsists of one or more nucleoside analogs (e.g., 2-aminoadenosine,2-thiothymidine, inosine, pyrrolo-pyrimidine, 3-methyl adenosine,5-methylcytidine, C-5 propynyl-cytidine, C-5 propynyl-uridine,2-aminoadenosine, C5-bromouridine, C5-fluorouridine, C5-iodouridine,C5-propynyl-uridine, C5-propynyl-cytidine, C5-methylcytidine,2-aminoadenosine, 7-deazaadenosine, 7-deazaguanosine, 8-oxoadenosine,8-oxoguanosine, O(6)-methylguanine, 2-thiocytidine, methylated bases,intercalated bases, and combinations thereof). In some embodiments, a“nucleic acid” comprises one or more modified sugars (e.g.,2′-fluororibose, ribose, 2′-deoxyribose, arabinose, and hexose) ascompared with those in natural nucleic acids. In some embodiments, a“nucleic acid” has a nucleotide sequence that encodes a functional geneproduct such as an RNA or protein. In some embodiments, a “nucleic acid”includes one or more introns. In some embodiments, a “nucleic acid”includes one or more exons. In some embodiments, a “nucleic acid” isprepared by one or more of isolation from a natural source, enzymaticsynthesis by polymerization based on a complementary template (in vivoor in vitro), reproduction in a recombinant cell or system, and chemicalsynthesis. In some embodiments, a “nucleic acid” is at least 3, 4, 5, 6,7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85,90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 20, 225, 250,275, 300, 325, 350, 375, 400, 425, 450, 475, 500, 600, 700, 800, 900,1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000 or more residueslong. In some embodiments, a “nucleic acid” is single stranded; in someembodiments, a “nucleic acid” is double stranded. In some embodiments, a“nucleic acid” has a nucleotide sequence comprising at least one elementthat encodes, or is the complement of a sequence that encodes, apolypeptide. In some embodiments, a “nucleic acid” has enzymaticactivity.

The phrase “operably linked”, as used herein, includes a juxtapositionwherein the components described are in a relationship permitting themto function in their intended manner. A control sequence “operablylinked” to a coding sequence is ligated in such a way that expression ofthe coding sequence is achieved under conditions compatible with thecontrol sequences. “Operably linked” sequences include both expressioncontrol sequences that are contiguous with the gene of interest andexpression control sequences that act in trans or at a distance tocontrol the gene of interest. The term “expression control sequence”, asused herein, includes polynucleotide sequences, which are necessary toeffect the expression and processing of coding sequences to which theyare ligated. “Expression control sequences” include: appropriatetranscription initiation, termination, promoter and enhancer sequences;efficient RNA processing signals such as splicing and polyadenylationsignals; sequences that stabilize cytoplasmic mRNA; sequences thatenhance translation efficiency (i.e., Kozak consensus sequence);sequences that enhance protein stability; and when desired, sequencesthat enhance protein secretion. The nature of such control sequencesdiffers depending upon the host organism. For example, in prokaryotes,such control sequences generally include promoter, ribosomal bindingsite, and transcription termination sequence, while in eukaryotes;typically, such control sequences include promoters and transcriptiontermination sequence. The term “control sequences” is intended toinclude components whose presence is essential for expression andprocessing, and can also include additional components whose presence isadvantageous, for example, leader sequences and fusion partnersequences.

The term “polypeptide”, as used herein, includes any polymeric chain ofamino acids. In some embodiments, a polypeptide has an amino acidsequence that occurs in nature. In some embodiments, a polypeptide hasan amino acid sequence that does not occur in nature. In someembodiments, a polypeptide has an amino acid sequence that containsportions that occur in nature separately from one another (i.e., fromtwo or more different organisms, for example, human and non-humanportions). In some embodiments, a polypeptide has an amino acid sequencethat is engineered in that it is designed and/or produced through actionof the hand of man.

“Prevent” or “prevention”, as used herein when used in connection withthe occurrence of a disease, disorder, and/or condition, includesreducing the risk of developing the disease, disorder and/or conditionand/or to delaying onset of one or more characteristics or symptoms ofthe disease, disorder or condition. Prevention may be consideredcomplete when onset of a disease, disorder or condition has been delayedfor a predefined period of time.

The term “recombinant”, as used herein, is intended to refer topolypeptides (e.g., PD-L1 polypeptides as described herein) that aredesigned, engineered, prepared, expressed, created or isolated byrecombinant means, such as polypeptides expressed using a recombinantexpression vector transfected into a host cell, polypeptides isolatedfrom a recombinant, combinatorial human polypeptide library (HoogenboomH. R., 1997 TIB Tech. 15:62-70; Hoogenboom H., and Chames P., 2000,Immunology Today 21:371-378; Azzazy H., and Highsmith W. E., 2002, Clin.Biochem. 35:425-445; Gavilondo J. V., and Larrick J. W., 2002,BioTechniques 29:128-145), antibodies isolated from an animal (e.g., amouse) that is transgenic for human immunoglobulin genes (see e.g.,Taylor, L. D., et al., 1992, Nucl. Acids Res. 20:6287-6295; Little M. etal., 2000, Immunology Today 21:364-370; Kellermann S. A. and Green L.L., 2002, Current Opinion in Biotechnology 13:593-597; Murphy, A. J., etal., 2014, Proc. Natl. Acad. Sci. U.S.A. 111(14):5153-5158) orpolypeptides prepared, expressed, created or isolated by any other meansthat involves splicing selected sequence elements to one another. Insome embodiments, one or more of such selected sequence elements isfound in nature. In some embodiments, one or more of such selectedsequence elements is designed in silico. In some embodiments, one ormore such selected sequence elements result from mutagenesis (e.g., invivo or in vitro) of a known sequence element, e.g., from a natural orsynthetic source. For example, in some embodiments, a recombinantpolypeptide comprises sequences found in the genome of a source organismof interest (e.g., human, mouse, etc.). In some embodiments, arecombinant polypeptide comprises sequences that occur in natureseparately from one another (i.e., from two or more different organisms,for example, human and non-human portions) in two different organisms(e.g., a human and a non-human organism). In some embodiments, arecombinant polypeptide has an amino acid sequence that resulted frommutagenesis (e.g., in vitro or in vivo, for example in a non-humananimal), so that the amino acid sequences of the recombinantpolypeptides are sequences that, while originating from and related topolypeptides sequences, may not naturally exist within the genome of anon-human animal in vivo.

The term “replacement” is used herein to refer to a process throughwhich a “replaced” nucleic acid sequence (e.g., a gene) found in a hostlocus (e.g., in a genome) is removed from that locus, and a different,“replacement” nucleic acid is located in its place. In some embodiments,the replaced nucleic acid sequence and the replacement nucleic acidsequences are comparable to one another in that, for example, they arehomologous to one another and/or contain corresponding elements (e.g.,protein-coding elements, regulatory elements, etc.). In someembodiments, a replaced nucleic acid sequence includes one or more of apromoter, an enhancer, a splice donor site, a splice receiver site, anintron, an exon, an untranslated region (UTR); in some embodiments, areplacement nucleic acid sequence includes one or more coding sequences.In some embodiments, a replacement nucleic acid sequence is a homolog ofthe replaced nucleic acid sequence. In some embodiments, a replacementnucleic acid sequence is an ortholog of the replaced sequence. In someembodiments, a replacement nucleic acid sequence is or comprises a humannucleic acid sequence. In some embodiments, including where thereplacement nucleic acid sequence is or comprises a human nucleic acidsequence, the replaced nucleic acid sequence is or comprises a rodentsequence (e.g., a mouse or rat sequence). The nucleic acid sequence soplaced may include one or more regulatory sequences that are part ofsource nucleic acid sequence used to obtain the sequence so placed(e.g., promoters, enhancers, 5′- or 3′-untranslated regions, etc.). Forexample, in various embodiments, the replacement is a substitution of anendogenous sequence with a heterologous sequence that results in theproduction of a gene product from the nucleic acid sequence so placed(comprising the heterologous sequence), but not expression of theendogenous sequence; the replacement is of an endogenous genomicsequence with a nucleic acid sequence that encodes a protein that has asimilar function as a protein encoded by the endogenous sequence (e.g.,the endogenous genomic sequence encodes a PD-L1 protein, and the DNAfragment encodes one or more human PD-L1 proteins). In variousembodiments, an endogenous gene or fragment thereof is replaced with acorresponding human gene or fragment thereof. A corresponding human geneor fragment thereof is a human gene or fragment that is an ortholog of,or is substantially similar or the same in structure and/or function, asthe endogenous gene or fragment thereof that is replaced.

The term “reference” is used herein to describe a standard or controlagent, animal, cohort, individual, population, sample, sequence or valueagainst which an agent, animal, cohort, individual, population, sample,sequence or value of interest is compared. In some embodiments, areference agent, animal, cohort, individual, population, sample,sequence or value is tested and/or determined substantiallysimultaneously with the testing or determination of the agent, animal,cohort, individual, population, sample, sequence or value of interest.In some embodiments, a reference agent, animal, cohort, individual,population, sample, sequence or value is a historical reference,optionally embodied in a tangible medium. In some embodiments, areference may refer to a control. As used herein, a “reference” mayinclude a “reference animal”. A “reference animal” may have amodification as described herein, a modification that is different asdescribed herein or no modification (i.e., a wild-type animal).Typically, as would be understood by those skilled in the art, areference agent, animal, cohort, individual, population, sample,sequence or value is determined or characterized under conditionscomparable to those utilized to determine or characterize the agent,animal (e.g., a mammal), cohort, individual, population, sample,sequence or value of interest.

The term “substantially”, as used herein, includes the qualitativecondition of exhibiting total or near-total extent or degree of acharacteristic or property of interest. One of ordinary skill in thebiological arts will understand that biological and chemical phenomenararely, if ever, go to completion and/or proceed to completeness orachieve or avoid an absolute result. The term “substantially” istherefore used herein to capture the potential lack of completenessinherent in many biological and chemical phenomena.

The phrase “substantial homology”, as used herein, includes a comparisonbetween amino acid or nucleic acid sequences. As will be appreciated bythose of ordinary skill in the art, two sequences are generallyconsidered to be “substantially homologous” if they contain homologousresidues in corresponding positions. Homologous residues may beidentical residues. Alternatively, homologous residues may benon-identical residues will appropriately similar structural and/orfunctional characteristics. For example, as is well known by those ofordinary skill in the art, certain amino acids are typically classifiedas “hydrophobic” or “hydrophilic” amino acids, and/or as having “polar”or “non-polar” side chains. Substitution of one amino acid for anotherof the same type may often be considered a “homologous” substitution.Typical amino acid categorizations are summarized in Tables 1 and 2.

TABLE 1 Alanine Ala A Nonpolar Neutral 1.8 Arginine Arg R Polar Positive−4.5 Asparagine Asn N Polar Neutral −3.5 Aspartic acid Asp D PolarNegative −3.5 Cysteine Cys C Nonpolar Neutral 2.5 Glutamic acid Glu EPolar Negative −3.5 Glutamine Gln Q Polar Neutral −3.5 Glycine Gly GNonpolar Neutral −0.4 Histidine His H Polar Positive −3.2 Isoleucine IleI Nonpolar Neutral 4.5 Leucine Leu L Nonpolar Neutral 3.8 Lysine Lys KPolar Positive −3.9 Methionine Met M Nonpolar Neutral 1.9 PhenylalaninePhe F Nonpolar Neutral 2.8 Proline Pro P Nonpolar Neutral −1.6 SerineSer S Polar Neutral −0.8 Threonine Thr T Polar Neutral −0.7 TryptophanTrp W Nonpolar Neutral −0.9 Tyrosine Tyr Y Polar Neutral −1.3 Valine ValV Nonpolar Neutral 4.2

TABLE 2 Ambiguous Amino Acids 3-Letter 1-Letter Asparagine or asparticacid Asx B Glutamine or glutamic acid Glx Z Leucine or Isoleucine Xle JUnspecified or unknown amino acid Xaa X

As is well known in this art, amino acid or nucleic acid sequences maybe compared using any of a variety of algorithms, including thoseavailable in commercial computer programs such as BLASTN for nucleotidesequences and BLASTP, gapped BLAST, and PSI-BLAST for amino acidsequences. Exemplary such programs are described in Altschul, S. F. etal., 1990, J. Mol. Biol., 215(3): 403-410; Altschul, S. F. et al., 1997,Methods in Enzymology; Altschul, S. F. et al., 1997, Nucleic Acids Res.,25:3389-3402; Baxevanis, A. D., and B. F. F. Ouellette (eds.)Bioinformatics: A Practical Guide to the Analysis of Genes and Proteins,Wiley, 1998; and Misener et al. (eds.) Bioinformatics Methods andProtocols (Methods in Molecular Biology, Vol. 132), Humana Press, 1998.In addition to identifying homologous sequences, the programs mentionedabove typically provide an indication of the degree of homology. In someembodiments, two sequences are considered to be substantially homologousif at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 910%, 92%, 93%,94%, 95%, 96%, 97%, 980%, 99% or more of their corresponding residuesare homologous over a relevant stretch of residues. In some embodiments,the relevant stretch is a complete sequence. In some embodiments, therelevant stretch is at least 9, 10, 11, 12, 13, 14, 15, 16, 17 or moreresidues. In some embodiments, the relevant stretch includes contiguousresidues along a complete sequence. In some embodiments, the relevantstretch includes discontinuous residues along a complete sequence, forexample, noncontiguous residues brought together by the foldedconformation of a polypeptide or a portion thereof. In some embodiments,the relevant stretch is at least 10, 15, 20, 25, 30, 35, 40, 45, 50, ormore residues.

The phrase “substantial identity”, as used herein, includes a comparisonbetween amino acid or nucleic acid sequences. As will be appreciated bythose of ordinary skill in the art, two sequences are generallyconsidered to be “substantially identical” if they contain identicalresidues in corresponding positions. As is well known in this art, aminoacid or nucleic acid sequences may be compared using any of a variety ofalgorithms, including those available in commercial computer programssuch as BLASTN for nucleotide sequences and BLASTP, gapped BLAST, andPSI-BLAST for amino acid sequences. Exemplary such programs aredescribed in Altschul, S. F. et al., 1990, J. Mol. Biol., 215(3):403-410; Altschul, S. F. et al., 1997, Methods in Enzymology; Altschul,S. F. et al., 1997, Nucleic Acids Res., 25:3389-3402; Baxevanis, A. D.,and B. F. F. Ouellette (eds.) Bioinformatics: A Practical Guide to theAnalysis of Genes and Proteins, Wiley, 1998; and Misener et al. (eds.)Bioinformatics Methods and Protocols (Methods in Molecular Biology, Vol.132), Humana Press, 1998. In addition to identifying identicalsequences, the programs mentioned above typically provide an indicationof the degree of identity. In some embodiments, two sequences areconsidered to be substantially identical if at least 500, 55%, 60%, 65%,70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% ormore of their corresponding residues are identical over a relevantstretch of residues. In some embodiments, the relevant stretch is acomplete sequence. In some embodiments, the relevant stretch is at least10, 15, 20, 25, 30, 35, 40, 45, 50, or more residues.

The phrase “targeting vector” or “targeting construct”, as used herein,includes a polynucleotide molecule that comprises a targeting region. Atargeting region comprises a sequence that is identical or substantiallyidentical to a sequence in a target cell, tissue or animal and providesfor integration of the targeting construct into a position within thegenome of the cell, tissue or animal via homologous recombination.Targeting regions that target using site-specific recombinaserecognition sites (e.g., loxP or Frt sites) are also included. In someembodiments, a targeting construct of the present invention furthercomprises a nucleic acid sequence or gene of particular interest, aselectable marker, control and or regulatory sequences, and othernucleic acid sequences that allow for recombination mediated throughexogenous addition of proteins that aid in or facilitate recombinationinvolving such sequences. In some embodiments, a targeting construct ofthe present invention further comprises a gene of interest in whole orin part, wherein the gene of interest is a heterologous gene thatencodes a protein, in whole or in part, that has a similar function as aprotein encoded by an endogenous sequence. In some embodiments, atargeting construct of the present invention further comprises ahumanized gene of interest, in whole or in part, wherein the humanizedgene of interest encodes a protein, in whole or in part, that has asimilar function as a protein encoded by the endogenous sequence.

The term “variant”, as used herein, includes an entity that showssignificant structural identity with a reference entity, but differsstructurally from the reference entity in the presence or level of oneor more chemical moieties as compared with the reference entity. In manyembodiments, a “variant” also differs functionally from its referenceentity. In general, whether a particular entity is properly consideredto be a “variant” of a reference entity is based on its degree ofstructural identity with the reference entity. As will be appreciated bythose skilled in the art, any biological or chemical reference entityhas certain characteristic structural elements. A “variant”, bydefinition, is a distinct chemical entity that shares one or more suchcharacteristic structural elements. To give but a few examples, a smallmolecule may have a characteristic core structural element (e.g., amacrocycle core) and/or one or more characteristic pendent moieties sothat a variant of the small molecule is one that shares the corestructural element and the characteristic pendent moieties but differsin other pendent moieties and/or in types of bonds present (single vs.double, E vs. Z, etc.) within the core, a polypeptide may have acharacteristic sequence element comprised of a plurality of amino acidshaving designated positions relative to one another in linear orthree-dimensional space and/or contributing to a particular biologicalfunction, a nucleic acid may have a characteristic sequence elementcomprised of a plurality of nucleotide residues having designatedpositions relative to on another in linear or three-dimensional space.For example, a “variant polypeptide” may differ from a referencepolypeptide as a result of one or more differences in amino acidsequence and/or one or more differences in chemical moieties (e.g.,carbohydrates, lipids, etc.) covalently attached to the polypeptidebackbone. In some embodiments, a “variant polypeptide” shows an overallsequence identity with a reference polypeptide that is at least 85%,86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or 99%.Alternatively or additionally, in some embodiments, a “variantpolypeptide” does not share at least one characteristic sequence elementwith a reference polypeptide. In some embodiments, the referencepolypeptide has one or more biological activities. In some embodiments,a “variant polypeptide” shares one or more of the biological activitiesof the reference polypeptide. In some embodiments, a “variantpolypeptide” lacks one or more of the biological activities of thereference polypeptide. In some embodiments, a “variant polypeptide”shows a reduced level of one or more biological activities as comparedwith the reference polypeptide. In many embodiments, a polypeptide ofinterest is considered to be a “variant” of a parent or referencepolypeptide if the polypeptide of interest has an amino acid sequencethat is identical to that of the parent but for a small number ofsequence alterations at particular positions. Typically, fewer than 20%,15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2% of the residues in the variantare substituted as compared with the parent. In some embodiments, a“variant” has 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 substituted residue ascompared with a parent. Often, a “variant” has a very small number(e.g., fewer than 5, 4, 3, 2, or 1) number of substituted functionalresidues (i.e., residues that participate in a particular biologicalactivity). Furthermore, a “variant” typically has not more than 5, 4, 3,2, or 1 additions or deletions, and often has no additions or deletions,as compared with the parent. Moreover, any additions or deletions aretypically fewer than about 25, about 20, about 19, about 18, about 17,about 16, about 15, about 14, about 13, about 10, about 9, about 8,about 7, about 6, and commonly are fewer than about 5, about 4, about 3,or about 2 residues. In some embodiments, the parent or referencepolypeptide is one found in nature. As will be understood by those ofordinary skill in the art, a plurality of variants of a particularpolypeptide of interest may commonly be found in nature, particularlywhen the polypeptide of interest is an infectious agent polypeptide.

The term “vector”, as used herein, includes a nucleic acid moleculecapable of transporting another nucleic acid to which it is associated.In some embodiment, vectors are capable of extra-chromosomal replicationand/or expression of nucleic acids to which they are linked in a hostcell such as a eukaryotic and/or prokaryotic cell. Vectors capable ofdirecting the expression of operatively linked genes are referred toherein as “expression vectors.”

The term “wild-type”, as used herein, has its art-understood meaningthat includes an entity having a structure and/or activity as found innature in a “normal” (as contrasted with mutant, diseased, altered,etc.) state or context. Those of ordinary skill in the art willappreciate that wild-type genes and polypeptides often exist in multipledifferent forms (e.g., alleles).

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The present invention provides, among other things, improved and/orengineered non-human animals having humanized genetic material encodinga Programmed death-ligand 1 (PD-L1) polypeptide for determining thetherapeutic efficacy of PD-L1 modulators (e.g., an anti-PD-L1 antibody)for the treatment of cancer, autoimmune diseases and infectiouspathogens, as well as assays in immune cell responses and function. Itis contemplated that such non-human animals provide an improvement indetermining the therapeutic efficacy of PD-L1 modulators and theirpotential for PD-1:PD-L1 (or PD-L1:B7-1) blockade. Therefore, thepresent invention is particularly useful for the development ofanti-PD-L1 and, in some embodiments, anti-PD-1 therapies, for thetreatment of various cancers, autoimmune diseases as well as foraugmenting immune responses to treat and/or ameliorate infectiousetiologies. In particular, the present invention encompasses thehumanization of a rodent CD274 gene resulting in expression of ahumanized PD-L1 polypeptide on the surface of cells of the non-humananimal. Such humanized PD-L1 non-human animals have the capacity toprovide a source of human PD-L1 cells for determining the efficacy ofanti-PD-L1 therapeutics to promote anti-tumor immune responses. Suchhumanized PD-L1 non-human animals also have the capacity to provide asource of human PD-L1 cells for determining the efficacy of anti-PD-L1therapeutics to ameliorate an autoimmune disease, disorder, orcondition. Further, such humanized PD-L1 non-human animals provide an invivo system for the screening and development of anti-PD-L1 therapiesfor the treatment of various cancers, autoimmune diseases and infectiousdiseases. In some embodiments, treatment efficacy may be demonstrated innon-human animals of the present invention by a decrease in ordisappearance of signs and/or symptoms of the disease, disorder, orcondition; in some embodiments, a decrease in or disappearance of some,but not all, signs and symptoms of the disease, disorder, or condition;in some embodiments, a decrease in or disappearance of all signs andsymptoms of the disease, disorder, or condition, although the disease,disorder, or condition still may be in the body of the non-human animal.In various embodiments, the disease, disorder or condition is associatedwith a cancer. In various embodiments, the disease, disorder orcondition is associated with an autoimmune disease, disorder orcondition. In various embodiments, the disease, disorder or condition isassociated with an infectious pathogen (e.g., a bacterium).

In some embodiments, non-human animals of the present inventiondemonstrate modulated immune responses via blockade of PD-1:PD-L1signaling through the humanized PD-L1 polypeptide expressed on thesurface of cells of the non-human animal. In some embodiments, humanizedPD-L1 polypeptides have a sequence corresponding to the immunoglobulin Vand C domains, in whole or in part, of a human PD-L1 polypeptide. Insome embodiments, humanized PD-L1 polypeptides have a sequencecorresponding to substantially all of the extracellular domain of ahuman PD-L1 polypeptide. In some embodiments, humanized PD-L1polypeptides have a sequence corresponding to the cytoplasmic domain ofa rodent PD-L1 polypeptide; in some embodiments, a sequencecorresponding to the transmembrane and cytoplasmic domains of a rodentPD-L1 polypeptide. In some embodiments, humanized PD-L1 polypeptideshave a sequence corresponding to amino acid residues 19-238 (or 19-227,or 19-131) of a human PD-L1 polypeptide. In some embodiments, non-humananimals of the present invention comprise a CD274 gene that containsgenetic material from the non-human animal and a heterologous species(e.g., a human). In some embodiments, non-human animals of the presentinvention comprise a humanized CD274 gene, wherein the humanized CD274gene comprises exon 3, exon 4, and exon 5 in whole or in part, of ahuman CD274 gene. In some certain embodiments, non-human animals of thepresent invention comprise a humanized CD274 gene, wherein the humanizedCD274 gene comprises about 4,494 bp of a human CD274 gene correspondingto exon 3 and about 4,160 bp of human genomic sequence 3′ of exon 3. Insome certain embodiments, non-human animals of the present inventioncomprise a humanized CD274 gene, wherein the humanized CD274 genecomprises about 3,950 bp of a human CD274 gene corresponding to about1,253 bp of human genomic sequence 5′ of exon 4, exon 4, intron 4 andthe first 32 bp of exon 5 of a human CD274 gene. In some certainembodiments, non-human animals of the present invention comprise ahumanized CD274 gene, wherein the humanized CD274 gene comprises about4,494 bp and about 3,950 bp of a human CD274 gene juxtaposed with asite-specific recombination site (e.g., a loxP site), which 4,494 bp and3,950 bp correspond to exon 3, exon 4 and the first 32 bp of exon 5 of ahuman CD274 gene. In some certain embodiments, non-human animals of thepresent invention comprise a humanized CD274 gene, wherein the humanizedCD274 gene comprises about 8,444 bp of a human CD274 gene correspondingto exon 3, exon 4 and the first 32 bp of exon 5 of a human CD274 gene.In some embodiments, non-human animals (e.g., rodents such as mice orrats) of the present invention comprise a humanized CD274 gene, whereinthe humanized CD274 gene comprises exon 3, exon 4 and a portion of exon5 of a human CD274 gene, operably linked to exons 1, 2, a portion ofexon 5, exon 6 and 7 of a non-human Cd274 gene (e.g., an endogenousnon-human Cd274 gene); and in specific embodiments, the humanized CD274gene encodes a humanized PD-L1 polypeptide that includes all orsubstantially all of the extracellular domain of a human PD-L1polypeptide, and all or substantially all of the transmembrane andcytoplasmic domains of a non-human PD-L1 polypeptide. In some certainembodiments, non-human animals of the present invention comprise ahumanized CD274 gene depicted in FIG. 2.

Various aspects of the invention are described in detail in thefollowing sections. The use of sections is not meant to limit theinvention. Each section can apply to any aspect of the invention.Throughout this application, the use of “or” means “and/or” unlessstated otherwise.

Cluster of Differentiation 274 (CD274) Gene

CD274, which encodes a polypeptide termed Programmed cell death ligand 1(PD-L1, also referred to as B7-H1), was discovered by searching thehuman expressed sequence tag (EST) database using B7 family members B7-1and B7-2 (Dong, H. et al., 1999, Nature Med. 5(12):1365-1369; Freeman,G. J. et al., 2000, J. Exp. Med. 192(7):1027-1034). The CD274 geneconsists of seven exons that each encode distinct portions of the PD-L1polypeptide; exon 1: non-coding and contains 5′UTR; exon 2: signalsequence; exon 3: immunoglobulin V (IgV) domain; exon 4: immunoglobulinC (IgC) domain; exon 5: C-terminal part of the extracellular domain andtransmembrane domain; exon 6: intracellular domain; and exon 7: ˜6 aminoacid residues of the intracellular domain and the 3′UTR. The PD-L1polypeptide shares a common structural organization with other B7 familymembers (B7-1 and B7-2) despite a low percent sequence identity (˜20%).In contrast, the PD-L1 polypeptide sequences of mouse and man shareabout 70% sequence identity (Freeman, G. J. et al., supra). PD-L1 isstrongly expressed in heart, skeletal muscle, placenta, and lung, weaklyexpressed in thymus, spleen, kidney and liver, and not expressed inbrain, colon or small intestine (Dong, H. et al., supra). Further, PD-L1is constitutively expressed on T cells, B cells, myeloid cells (e.g.,dendritic cells, macrophages, mast cells, etc.) and keratinocytes inmouse, whereas expression in the same cells in humans has been reportedafter activation (e.g., reviewed in Keir, M. E., et al., 2008, Annu.Rev. Immunol. 26:677-704). Indeed, the CD274 promoter for both mouse andhuman genes has been reported to contain binding sites for interferonregulatory factor 1 (IRF-1), which has been suggested as beingresponsible for PD-L1 upregulation in human cancer cells (Lee, S. J. etal., 2006, FEBS Lett. 580(3):755-762). PD-L1 splice variants have beenreported (see, e.g., below and He, X. H. et al., 2005, Acta PharmacolSin. 26(4):462-468), however, no causative relationship with any diseasehas yet been discovered. PD-L1 binds PD-1 exclusively without anyinteractions with other proteins structurally similar to PD-1 (CTLA4,CD28, ICOS; see Dong. Dong, H. et al. and Freeman, G. J. et al., supra).PD-L1 engagement with PD-1 leads to a variety of stimulatory orinhibitory functions in immune cells, some of which include cellproliferation, cytokine production, and T cell receptor and B cellreceptor signaling. PD-L1 (as well as PD-L2) has also been suggested tobe involved in bidirectional signaling (e.g., see Dong, H. et al., 2003,J. Clin. Invest. 111:363-370; Kuipers, H. et al., 2006, Eur. J. Immunol.36:2472-2782). Interestingly, PD-L1 has been shown to bind B7-1 (CD80),a ligand for CD28, although no interaction with CD28 itself has beenreported (Butte, M. J. et al., 2007, Immunity 27:111-122). This uniqueinteraction with B7-1 has been particularly important for itsimplications in the regulation of T cell responses and tolerance.Indeed, due to multiple functional outcomes provided by itscostimulatory and coinhibitory functions, PD-L1 has attracted muchinterest as a potential target for treatment of autoimmune andinflammatory diseases as well as the treatment of cancer. In fact,anti-PD-L1 therapy is currently being tested in human clinical trials(see e.g., Pedoeem, A. et al., 2014, Clin. Immunol. 153:145-152; andPhilips, G. K. and Atkins, M., 2014, Intern. Immunol. 8 pages).

A more thorough and detailed understanding of PD-L1-mediated functionsacross many of the cell types in which it is expressed (e.g.,non-lymphoid cells) and the unique interactions with other B7 familymembers is needed to develop practical targeted therapies for treatmentof cancer and autoimmunity in the future.

CD274 and PD-L1 (B7-H1) Sequences

Exemplary murine, human and humanized CD274 and PD-L1 sequences are setforth in FIG. 6. Exemplary human nucleic acid sequences for humanizationof a non-human CD274 gene are also set forth in FIG. 6. For mRNAsequences, bold font indicates coding sequence and consecutive exons,where indicated, are separated by alternating underlined text, forhumanized mRNA sequences, human sequences are contained withinparentheses. For protein sequences, signal peptides are underlined,extracellular sequences are bold font, immunoglobulin V (IgV) domainsequences are within parentheses, and intracellular sequences areitalicized; for humanized protein sequences, non-human sequences areindicated in regular font, human sequences are indicated in bold font.

CD274 transcript variants are known in the art. One transcript variantlacks an in-frame exon in the 5′ coding region as compared to thecanonical sequence (see FIG. 6) and results in a deletion of residues17-130 (i.e., the IgV domain plus ˜5 amino acid residues). The mRNA andprotein sequences of this variant can be found at Genbank accessionnumbers NM_001267706.1 and NP_001254635.1, respectively, herebyincorporated by reference. Another variant encodes a soluble proteinhaving a K178D substitution and a deletion of residues 179-290. The mRNAand protein sequences of this variant can be found at Genbank accessionnumbers XM_006716759.1 and XP_006716822.1, respectively, herebyincorporated by reference. A third variant has been described(NR_052005.1) to lack an alternate internal segment as compared to thecanonical sequence and, therefore, is represented as a non-codingvariant because the use of the 5′-most supported translation start codonrenders the transcript a candidate for nonsense-mediated mRNA decay(NMD). Other isoforms are described in WO 2014/197369, which is herebyincorporated by reference.

Humanized CD274 Non-Human Animals

Non-human animals are provided that express humanized PD-L1 polypeptideson the surface of cells of the non-human animals resulting from agenetic modification of an endogenous locus (e.g., a CD274 locus) of thenon-human animal that encodes a PD-L1 polypeptide. Suitable examplesdescribed herein include rodents, in some embodiments, mice.

A humanized CD274 gene, in some embodiments, comprises genetic materialfrom a heterologous species (e.g., humans), wherein the humanized CD274gene encodes a PD-L1 polypeptide that comprises the encoded portion ofthe genetic material from the heterologous species. In some embodiments,a humanized CD274 gene of the present invention comprises genomic DNA ofa heterologous species that encodes the extracellular portion of a PD-L1polypeptide that is expressed on the plasma membrane of a cell.Non-human animals, embryos, cells and targeting constructs for makingnon-human animals, non-human embryos, and cells containing saidhumanized CD274 gene are also provided.

In some embodiments, an endogenous CD274 gene is deleted. In someembodiments, an endogenous CD274 gene is altered, wherein a portion ofthe endogenous CD274 gene is replaced with a heterologous sequence(e.g., a human CD274 sequence, in whole or in part). In someembodiments, all or substantially all of an endogenous CD274 gene isreplaced with a heterologous gene (e.g., a human CD274 gene). In someembodiments, a portion of a heterologous CD274 gene is inserted into anendogenous non-human CD274 gene at an endogenous CD274 locus. In someembodiments, the heterologous gene is a human gene. In some embodiments,the modification or humanization is made to one of the two copies of theendogenous CD274 gene, giving rise to a non-human animal that isheterozygous with respect to the humanized CD274 gene. In otherembodiments, a non-human animal is provided that is homozygous for ahumanized CD274 gene.

In various aspects, a non-human animal contains a human CD274 gene, inwhole or in part, at an endogenous non-human CD274 locus. In someembodiments, a non-human animal contains a human CD274 gene, at alocation outside of an endogenous non-human CD274 locus. Thus, suchnon-human animals can be described as having a heterologous CD274 gene.The replaced, inserted, modified or altered CD274 gene at the endogenousCD274 locus (or outside the endogenous CD274 locus) or a polypeptideexpressed from such gene (or expressed from elsewhere in the genome ofthe non-human animal) can be detected using a variety of methodsincluding, for example, PCR, Western blot, Southern blot, restrictionfragment length polymorphism (RFLP), or a gain or loss of allele assay.In some embodiments, the non-human animal is heterozygous with respectto the humanized CD274 gene.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a third exon having a sequenceat least 50% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%,92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more) identical to a thirdexon that appears in a human CD274 mRNA sequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a third exon having a sequencethat is substantially identical to a third exon that appears in a humanCD274 mRNA sequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a third exon having a sequencethat is identical to a third exon that appears in a human CD274 mRNAsequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a fourth exon having a sequenceat least 50% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%,92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more) identical to a fourthexon that appears in a human CD274 mRNA sequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a fourth exon having a sequencethat is substantially identical to a fourth exon that appears in a humanCD274 mRNA sequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a fourth exon having a sequencethat is identical to a fourth exon that appears in a human CD274 mRNAsequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a fifth exon having a sequenceat least 50% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%,92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more) identical to a fifthexon that appears in a humanized CD274 mRNA sequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a fifth exon having a sequencethat is substantially identical to a fifth exon that appears in ahumanized CD274 mRNA sequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a fifth exon having a sequencethat is identical to a fifth exon that appears in a humanized CD274 mRNAsequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a third, fourth and fifth exoneach having a sequence at least 50% (e.g., 50%, 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more)identical to a third, fourth and fifth exon that appear in a humanizedCD274 mRNA sequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a third, fourth and fifth exoneach having a sequence that is substantially identical to a third,fourth and fifth exon that appear in a humanized CD274 mRNA sequence ofFIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a third, fourth and fifth exoneach having a sequence that is identical to a third, fourth and fifthexon that appear in a humanized CD274 mRNA sequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a first, second, sixth andseventh exon each having a sequence at least 50% (e.g., 50%, 55%, 60%,65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%,99% or more) identical to a first, second, sixth and seventh exon thatappear in a mouse Cd274 mRNA sequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a first, second, sixth andseventh exon each having a sequence that is substantially identical to afirst, second, sixth and seventh exon that appear in a mouse Cd274 mRNAsequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a first, second, sixth andseventh exon each having a sequence that is identical to a first,second, sixth and seventh exon that appear in a mouse Cd274 mRNAsequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that comprises a sequence at least 50%(e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%,95%, 96%, 97%, 98%, 99% or more) identical to SEQ ID NO:12.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that comprises a sequence that issubstantially identical to SEQ ID NO:12.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that comprises a sequence that isidentical to SEQ ID NO:12.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that comprises a sequence at least 50%(e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%,95%, 96%, 97%, 98%, 99% or more) identical to SEQ ID NO: 13 or SEQ IDNO: 16.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that comprises a sequence that issubstantially identical to SEQ ID NO:13 or SEQ ID NO:16.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that comprises a sequence that isidentical to SEQ ID NO:13 or SEQ ID NO:16.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that comprises a first sequence at least50% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%,94%, 95%, 96%, 97%, 98%, 99% or more) identical to SEQ ID NO: 13 and asecond sequence at least 50% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%,85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more) identicalto SEQ ID NO: 16.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that comprises a first sequence that issubstantially identical to SEQ ID NO:13 and a second sequence that issubstantially identical to SEQ ID NO:16.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that comprises a first sequence that isidentical to SEQ ID NO: 13 and a second sequence that is identical toSEQ ID NO: 16.

In various embodiments, a humanized CD274 gene according to the presentinvention comprises SEQ ID NO: 13, SEQ ID NO: 16 and a site-specificrecombinase recognition site, wherein said site-specific recombinaserecognition site is located within an intron of said humanized CD274gene.

In various embodiments, a humanized CD274 gene according to the presentinvention comprises SEQ ID NO: 13, SEQ ID NO:16 and a loxP site, whereinsaid loxP site is located within an intron of said humanized CD274 gene.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that comprises an intron between a CD274exon 3 and a CD274 exon 4, wherein said intron comprises a sequence thatis substantially identical to SEQ ID NO:17.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that comprises an intron between a CD274exon 3 and a CD274 exon 4, wherein said intron comprises a sequence thatis identical to SEQ ID NO: 17.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that comprises SEQ ID NO: 12, SEQ ID NO:13, SEQ ID NO:16 and SEQ ID NO:17.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that comprises SEQ ID NO: 12, SEQ IDNO:13, SEQ ID NO:14, SEQ ID NO:15 and SEQ ID NO:16.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a nucleotide coding sequence(e.g., a cDNA sequence) at least 50% (e.g., 50%, 55%, 60%, 65%, 70%,75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more)identical to a nucleotide coding sequence that appears in a humanizedCD274 nucleotide coding sequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a nucleotide coding sequence(e.g., a cDNA sequence) that is substantially identical to a nucleotidecoding sequence that appears in a humanized CD274 nucleotide codingsequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention includes a CD274 gene that has a nucleotide coding sequence(e.g., a cDNA sequence) that is identical to a nucleotide codingsequence that appears in a humanized CD274 nucleotide coding sequence ofFIG. 6.

In various embodiments, a humanized CD274 mRNA sequence according to thepresent invention comprises a sequence at least 50% (e.g., 50%, 55%,60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%,98%, 99% or more) identical to a humanized CD274 mRNA sequence of FIG.6.

In various embodiments, a humanized CD274 mRNA sequence according to thepresent invention comprises a sequence that is substantially identicalto a humanized CD274 mRNA sequence of FIG. 6.

In various embodiments, a humanized CD274 mRNA sequence according to thepresent invention comprises a sequence that is identical to a humanizedCD274 mRNA sequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention encodes a PD-L1 polypeptide having an amino acid sequence atleast 50% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%,93%, 94%, 95%, 96%, 97%, 98%, 99% or more) identical to a PD-L1polypeptide sequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention encodes a PD-L1 polypeptide having an amino acid sequence thatis substantially identical to a PD-L1 polypeptide sequence of FIG. 6.

In various embodiments, a humanized CD274 gene according to the presentinvention encodes a PD-L1 polypeptide having an amino acid sequence thatis identical to a PD-L1 polypeptide sequence of FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has an extracellular portion having anamino acid sequence at least 50% (e.g., 50%, 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more)identical to an extracellular portion of a human PD-L1 polypeptide thatappears in FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has an extracellular portion having anamino acid sequence that is substantially identical to an extracellularportion of a human PD-L1 polypeptide that appears in FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has an extracellular portion having anamino acid sequence that is identical to an extracellular portion of ahuman PD-L1 polypeptide that appears in FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention comprises an amino acid sequence atleast 50% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%,93%, 940%, 95%, 96%, 97%, 98%, 99% or more) identical to amino acidresidues 19-131 that appears in a human or humanized PD-L1 polypeptideof FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention comprises an amino acid sequence that issubstantially identical to amino acid residues 19-131 that appears in ahuman or humanized PD-L1 polypeptide of FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention comprises an amino acid sequence that isidentical to amino acid residues 19-131 that appears in a human orhumanized PD-L1 polypeptide of FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention comprises an amino acid sequence atleast 50% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%,93%, 94%, 95%, 96%, 97%, 98%, 99% or more) identical to amino acidresidues 19-227 that appears in a human or humanized PD-L1 polypeptideof FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention comprises an amino acid sequence that issubstantially identical to amino acid residues 19-227 that appears in ahuman or humanized PD-L1 polypeptide of FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention comprises an amino acid sequence that isidentical to amino acid residues 19-227 that appears in a human orhumanized PD-L1 polypeptide of FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention comprises an amino acid sequence atleast 50% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%,93%, 94%, 95%, 96%, 97%, 98%, 99% or more) identical to amino acidresidues 19-238 that appears in a human or humanized PD-L1 polypeptideof FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention comprises an amino acid sequence that issubstantially identical to amino acid residues 19-238 that appears in ahuman or humanized PD-L1 polypeptide of FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention comprises an amino acid sequence that isidentical to amino acid residues 19-238 that appears in a human orhumanized PD-L1 polypeptide of FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has an immunoglobulin V (IgV) domainhaving an amino acid sequence at least 50% (e.g., 50%, 55%, 60%, 65%,70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% ormore) identical to an IgV domain of a human PD-L1 polypeptide thatappears in FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has an immunoglobulin V (IgV) domainhaving an amino acid sequence that is substantially identical to an IgVdomain of a human PD-L1 polypeptide that appears in FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has an immunoglobulin V (IgV) domainhaving an amino acid sequence that is identical to an IgV domain of ahuman PD-L1 polypeptide that appears in FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has an immunoglobulin V (IgV) domain andan immunoglobulin C (IgC) domain each having an amino acid sequence atleast 50% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%,93%, 94%, 95%, 96%, 97%, 98%, 99% or more) identical to an IgV domainand an IgC domain of a human PD-L1 polypeptide that appears in FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has an immunoglobulin V (IgV) domain andan immunoglobulin C (IgC) domain each having an amino acid sequence thatis substantially identical to an IgV domain and an IgC domain of a humanPD-L1 polypeptide that appears in FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has an immunoglobulin V (IgV) domain andan immunoglobulin C (IgC) domain each having an amino acid sequence thatis identical to an IgV domain and an IgC domain of a human PD-L1polypeptide that appears in FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has a transmembrane domain and anintracellular domain each having an amino acid sequence at least 50%(e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%,95%, 96%, 97%, 98%, 99% or more) identical to a transmembrane domain andan intracellular domain of a mouse PD-L1 polypeptide that appears inFIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has a transmembrane domain and anintracellular domain each having an amino acid sequence that issubstantially identical to a transmembrane domain and an intracellulardomain of a mouse PD-L1 polypeptide that appears in FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has a transmembrane domain and anintracellular domain each having an amino acid sequence that isidentical to a transmembrane domain and an intracellular domain of amouse PD-L1 polypeptide that appears in FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has an amino acid sequence at least 50%(e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%,95%, 96%, 97%, 98%, 99% or more) identical to an amino acid sequence ofa humanized PD-L1 polypeptide that appears in FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has an amino acid sequence that issubstantially identical to an amino acid sequence of a humanized PD-L1polypeptide that appears in FIG. 6.

In various embodiments, a PD-L1 polypeptide produced by a non-humananimal of the present invention has an amino acid sequence that isidentical to an amino acid sequence of a humanized PD-L1 polypeptidethat appears in FIG. 6.

Compositions and methods for making non-human animals that express ahumanized PD-L1 polypeptide, including specific polymorphic forms,allelic variants (e.g., single amino acid differences) or alternativelyspliced isoforms, are provided, including compositions and methods formaking non-human animals that express such polypeptides from a humanpromoter and a human regulatory sequence(s). In some embodiments,compositions and methods for making non-human animals that express suchpolypeptides from an endogenous promoter and an endogenous regulatorysequence(s) are also provided; in some embodiments, from an endogenousrodent promoter and an endogenous rodent regulatory sequence(s). Themethods include inserting the genetic material encoding a human PD-L1polypeptide (e.g., a human CD274 DNA sequence) in whole or in part at aprecise location in the genome of a non-human animal that corresponds toan endogenous CD274 gene thereby creating a humanized CD274 gene thatexpresses a PD-L1 polypeptide that is human in whole or in part.Alternatively, insertion of the genetic material encoding a human PD-L1polypeptide in whole or in part may be made at a random location in thegenome of a non-human animal, i.e., outside of an endogenous CD274 gene.In some embodiments, the methods include inserting genomic DNAcorresponding to exons 3-5 (or exons 3, 4 and a portion of exon 5) of ahuman CD274 gene into an endogenous CD274 gene of the non-human animalthereby creating a humanized gene that encodes a PD-L polypeptide thatcontains a human portion containing amino acids encoded by the insertedexons. In some embodiments, the methods include randomly insertinggenomic DNA corresponding to a full-length (or cDNA) human CD274 geneinto the genome of the non-human animal thereby creating a human CD274transgene that encodes a full-length human PD-L1 polypeptide.

Where appropriate, the coding region of the genetic material orpolynucleotide sequence(s) encoding a human PD-L1 polypeptide in wholeor in part may be modified to include codons that are optimized forexpression in the non-human animal (e.g., see U.S. Pat. Nos. 5,670,356and 5,874,304). Codon optimized sequences are synthetic sequences, andpreferably encode the identical polypeptide (or a biologically activefragment of a full length polypeptide which has substantially the sameactivity as the full length polypeptide) encoded by the non-codonoptimized parent polynucleotide. In some embodiments, the coding regionof the genetic material encoding a human PD-L1 polypeptide, in whole orin part, may include an altered sequence to optimize codon usage for aparticular cell type (e.g., a rodent cell). For example, the codons ofthe genomic DNA corresponding to exons 3-5 (or exons 3, 4 and a portionof exon 5) of a human CD274 gene to be inserted into an endogenous CD274gene of a non-human animal (e.g., a rodent) may be optimized forexpression in a cell of the non-human animal. Such a sequence may bedescribed as a codon-optimized sequence.

A humanized CD274 gene approach employs a relatively minimalmodification of the endogenous gene and results in naturalCD274-mediated (i.e., PD-L1-mediated) signal transduction in thenon-human animal, because, e.g., the genomic sequence of the CD274 geneis modified in a single fragment and therefore retains normalfunctionality by including necessary regulatory sequences and, in someembodiments, intron sequences. Thus, in such embodiments, the CD274 genemodification does not affect other surrounding genes or other endogenousCD274-interacting genes (e.g., Pdcd1, etc.). Further, in variousembodiments, the modification does not affect the assembly of afunctional PD-L1 transmembrane polypeptide on the plasma membrane andmaintains normal effector functions via binding and subsequent signaltransduction through the cytoplasmic portion of the polypeptide which isunaffected by the modification.

A schematic illustration (not to scale) of the genomic organization of arodent (e.g., mouse) Cd274 gene and a human CD274 gene is set forth inFIG. 1. Exemplary constructs for humanizing an endogenous rodent (e.g.,mouse) Cd274 gene using a genomic fragment containing exons 3, 4 and aportion of exon 5 of a human CD274 gene are set forth in FIG. 2. Asillustrated, genomic DNA containing exons 3, 4 and a portion of exon 5of a human CD274 gene is inserted into an endogenous rodent (e.g.,mouse) Cd274 gene locus by a targeting construct. This genomic DNAincludes the portion of the gene that encodes an extracellular portion(e.g., amino acid residues 19-238) of a human PD-L1 polypeptide. If sodesired, genomic DNA containing exons 3 and 4 of a human CD274 gene maybe inserted into an endogenous rodent (e.g., mouse) Cd274 gene locus bya targeting construct so to include the portion of the gene that encodesthe immunoglobulin V and C domains (e.g., amino acid residues 19-227) ofa human PD-L1 polypeptide. Alternatively, genomic DNA containing onlyexon 3 of a human CD274 gene may be inserted into an endogenous rodent(e.g., mouse) Cd274 gene locus by a targeting construct so to includeonly the portion of the gene that encodes the immunoglobulin V domain(e.g., amino acid residues 19-131) of a human PD-L1 polypeptide. Personsof skill upon reading this disclosure will understand that variousamounts of genetic material of a human CD274 gene may be inserted intothe genome of a non-human animal following the methodology describedherein depending on the encoded PD-L1 polypeptide that is desired.

A non-human animal (e.g., a mouse) having a humanized CD274 gene at theendogenous CD274 locus can be made by any method known in the art. Forexample, a targeting vector can be made that introduces a human CD274gene in whole or in part with a selectable marker gene. FIG. 2illustrates an endogenous Cd274 locus of a mouse genome comprising aninsertion of exons 3, 4 and a portion of exon 5 (about 32 bp) of a humanCD274 gene. As illustrated, the targeting construct contains a 5′homology arm containing sequence upstream of exon 3 of an endogenousmurine Cd274 gene (˜92.9 Kb), followed by a genomic DNA fragmentcontaining exon 3 of a human CD274 gene (˜4494 bp), a drug selectioncassette (e.g., a neomycin resistance gene flanked on both sides by loxPsequences; ˜5 Kb) in opposite transcriptional direction relative to theendogenous murine Cd274 gene, a genomic DNA fragment containing exons 4and a portion of exon 5 of a human CD274 gene (˜3950 bp), and a 3′homology arm containing a portion of exon 5 of an endogenous murineCd274 gene and genomic sequence downstream including exons 6 and 7(˜67.6 Kb). The targeting construct contains a self-deleting drugselection cassette (e.g., a neomycin resistance gene flanked by loxPsequences; see U.S. Pat. Nos. 8,697,851, 8,518,392 and 8,354,389, all ofwhich are hereby incorporated by reference). Upon homologousrecombination, exons 3, 4 and a portion of exon 5 of an endogenousmurine Cd274 gene are replaced by the sequence contained in thetargeting vector (i.e., exons 3, 4 and a portion of exon 5 of a humanCD274 gene) resulting in a deletion of about 8,964 bp. A humanized CD274gene is created resulting in a cell or non-human animal that expresses ahumanized PD-L1 polypeptide that contains amino acids encoded by theinserted genomic DNA of a human CD274 gene. The drug selection cassetteis removed in a development-dependent manner, i.e., progeny derived frommice whose germ line cells containing the humanized CD274 gene describedabove will shed the selectable marker from differentiated cells duringdevelopment.

Although embodiments employing a humanized CD274 gene in a mouse (i.e.,a mouse with a CD274 gene that encodes a PD-L1 polypeptide that includesa human portion and a mouse portion) are extensively discussed herein,other non-human animals that comprise a humanized CD274 gene are alsoprovided. In some embodiments, such non-human animals comprise ahumanized CD274 gene operably linked to an endogenous CD274 promoter. Insome certain embodiments, an endogenous CD274 promoter is an endogenousrodent promoter. In some embodiments, such non-human animals express ahumanized PD-L1 polypeptide from an endogenous locus, wherein thehumanized PD-L1 polypeptide comprises amino acid residues 19-238 (or19-227 or 19-131) of a human PD-L1 polypeptide. Such non-human animalsinclude any of those which can be genetically modified to express aPD-L1 polypeptide as disclosed herein, including, e.g., mammals, e.g.,mouse, rat, rabbit, pig, bovine (e.g., cow, bull, buffalo), deer, sheep,goat, chicken, cat, dog, ferret, primate (e.g., marmoset, rhesusmonkey), etc. Exemplary sequences of non-human CD274 orthologs include,e.g., chicken PD-L1 (XM_424811.3 and XP_424811.3), chimpanzee(XM_001140705.2 and XP 001140705.1), cow PD-L1 (NM_001163412.1 andNP_001 156884.1), and dog PD-L1 (XM 0.541302.3 and XP_541302.3), monkey(NM_001083889.1 and NP 001077358.1), and rat (NM_001191954.1 andNP_001178883.1), which are hereby incorporated by reference. Forexample, for those non-human animals for which suitable geneticallymodifiable ES cells are not readily available, other methods areemployed to make a non-human animal comprising the genetic modification.Such methods include, e.g., modifying a non-ES cell genome (e.g., afibroblast or an induced pluripotent cell) and employing somatic cellnuclear transfer (SCNT) to transfer the genetically modified genome to asuitable cell, e.g., an enucleated oocyte, and gestating the modifiedcell (e.g., the modified oocyte) in a non-human animal under suitableconditions to form an embryo (see, e.g., Wilmut, I. et al., 1997, Nature385:810-813; International Patent Application Publication Nos. WO97/07668 and WO 97/07669).

Methods for modifying a non-human animal genome (e.g., a pig, cow,rodent, chicken, etc. genome) include, e.g., employing a zinc fingernuclease (ZFN) or a transcription activator-like effector nuclease(TALEN) to modify a genome to include a humanized CD274 gene.

A non-human animal harboring a humanized CD274 gene as described hereinmay also be created by randomly introducing a CD274 nucleic acidsequence into the genome of a non-human animal as a transgene. Dependingupon context, cDNA or genomic human CD274 sequences may be employed. Forexample, intronic sequences and polyadenylation signals can be includedin the transgene to increase the efficiency and level of expression ofthe transgene. A tissue-specific regulatory sequence(s) can be operablylinked to a CD274 transgene to direct expression of a PD-L1 polypeptideto particular cell types. A constitutive promoter may be operably linkedto the CD274 nucleic acid sequence so that the encoded PD-L1 polypeptideis overexpressed (i.e., expressed at a higher level and/or in tissuesnot observed in a wild-type non-human animal).

A transgenic founder non-human animal can be identified based upon thepresence of a CD274 transgene in its genome and/or expression of PD-L1mRNA in tissues or cells of the non-human animal. A transgenic foundernon-human animal can then be used to breed additional non-human animalscarrying the CD274 transgene. Moreover, transgenic non-human animalscarrying a transgene encoding a human PD-L1 polypeptide, in whole or inpart, can further be bred to other transgenic non-human animals carryingother transgenes (e.g., a Pdcd1, or CD80 transgene).

Transgenic non-human animals may also be produced to contain selectedsystems that allow for regulated or directed expression of thetransgene. Exemplary systems include the Cre/loxP recombinase system ofbacteriophage P1 (see, e.g., Lakso, M. et al., 1992, Proc. Natl. Acad.Sci. USA 89:6232-6236) and the FLP/Frt recombinase system of S.cerevisiae (O'Gorman, S. et al, 1991, Science 251:1351-1355). Suchanimals can be provided through the construction of “double” transgenicanimals, e.g., by mating two transgenic animals, one containing atransgene encoding a selected polypeptide (e.g., a CD274 transgene) andthe other containing a transgene encoding a recombinase (e.g., a Crerecombinase).

The non-human animals of the present invention may be prepared asdescribed above, or using methods known in the art, to compriseadditional human or humanized genes, oftentimes depending on theintended use of the non-human animal. Genetic material of suchadditional human or humanized genes may be introduced through thefurther alteration of the genome of cells (e.g., embryonic stem cells)having the genetic modifications as described above or through breedingtechniques known in the art with other genetically modified strains asdesired. In some embodiments, non-human animals of the present inventionare prepared to further comprise one or more human or humanized genesselected from the B7 family of ligands and/or the CD28 family ofreceptors (e.g., Pdcd1 (PD-1), etc.). In some embodiments, non-humananimals of the present invention may be prepared by introducing atargeting vector, as described herein, into a cell from a modifiedstrain. In some embodiments, non-human animals of the present inventionare prepared to further comprise a human or humanized Programmed celldeath 1 (Pdcd1) gene. In some embodiments, non-human animals of thepresent invention comprise a humanized CD274 gene, as described herein,and genetic material from a heterologous species (e.g., humans), whereinthe genetic material encodes, in whole or in part, one or moreheterologous polypeptides selected from the B-7 family of ligands or theCD28 family of receptors. In some certain embodiments, non-human animalsof the present invention comprise a humanized CD274 gene as describedherein and genetic material from a heterologous species (e.g., humans),wherein the genetic material encodes, in whole or in part, aheterologous (e.g., human) PD-1 polypeptide. In some certainembodiments, non-human animals of the present invention further comprisea Pdcd1 gene that comprises an endogenous portion and a human portion,wherein the human portion encodes the extracellular domain of a humanPD-1 polypeptide and the endogenous portion encodes the intracellulardomain of an endogenous PD-1 polypeptide; in some embodiments, the humanand endogenous portions are operably linked to an endogenous Pdcd1promoter; in some embodiments, an endogenous rodent Pdcd1 promoter.

For example, as described herein, non-human animals comprising ahumanized CD274 gene may further comprise (e.g., via cross-breeding ormultiple gene targeting strategies) one or more modifications asdescribed in U.S. patent application Ser. No. 14/744,592, filed Jun. 19,2015, hereby incorporated by reference. In certain embodiments, a rodentcomprising a humanized CD274 gene (i.e., exon 3, 4 and a 5′ portion ofexon 5 of a human CD274 gene operably linked to exon 1, 2, a 3′ portionof exon 5, 6 and 7 of an endogenous rodent Cd274 gene so that thehumanized CD274 gene encodes a PD-L1 polypeptide having an extracellularportion from a human PD-L1 polypeptide and an intracellular portion froma rodent PD-L1 polypeptide) is crossed to a rodent comprising ahumanized Pdcd1 gene (e.g., exon 2 and a 5′ portion of exon 3 of a humanPDCD1 gene operably linked to exon 1, a 3′ portion of exon 3, 4 and 5 ofan endogenous rodent Pdcd1 gene so that the humanized Pdcd1 gene encodesa PD-1 polypeptide having an extracellular portion from a human PD-1polypeptide and an intracellular portion from a rodent PD-1 polypeptide;see, e.g., U.S. patent application Ser. No. 14/744,592, filed Jun. 19,2015, hereby incorporated by reference). In some embodiments, ahumanized Pdcd1 gene comprises non-human (e.g., rodent) Pdcd1 exons 1, 4and 5, a human Pdcd1 exon 2 and a Pdcd1 exon 3, which Pdcd1 exon 3comprises a human portion and a non-human portion, and wherein saidnon-human and human exons are operably linked. In some embodiments, ahuman portion of a Pdcd1 exon 3 includes nucleotides that encode a PD-1stalk sequence. In some embodiments, a human portion of a Pdcd1 exon 3includes about 71 bp of a human Pdcd1 exon 3. In some embodiments, anon-human portion of a Pdcd1 exon 3 includes nucleotides that encode atransmembrane sequence. In some embodiments, a non-human portion of aPdcd1 exon 3 includes about 91 bp of a rodent Pdcd1 exon 3. In specificembodiments, a humanized Pdcd1 gene encodes a humanized PD-1 polypeptidethat includes an extracellular portion (e.g., substantially the entireextracellular domain) from a human PD-1 polypeptide, a transmembraneportion (e.g., substantially the entire transmembrane domain), and anintracellular portion (e.g., (e.g., substantially the entireintracellular domain) from a rodent PD-1 polypeptide.

In some embodiments, a non-human animal of the present invention is amammal. In some embodiments, a non-human animal of the present inventionis a small mammal, e.g., of the superfamily Dipodoidea or Muroidea. Insome embodiments, a genetically modified animal of the present inventionis a rodent. In some embodiments, a rodent of the present invention isselected from a mouse, a rat, and a hamster. In some embodiments, arodent of the present invention is selected from the superfamilyMuroidea. In some embodiments, a genetically modified animal of thepresent invention is from a family selected from Calomyscidae (e.g.,mouse-like hamsters), Cricetidae (e.g., hamster, New World rats andmice, voles), Muridae (true mice and rats, gerbils, spiny mice, crestedrats), Nesomyidae (climbing mice, rock mice, white-tailed rats, Malagasyrats and mice), Platacanthomyidae (e.g., spiny dormice), and Spalacidae(e.g., mole rates, bamboo rats, and zokors). In some certainembodiments, a genetically modified rodent of the present invention isselected from a true mouse or rat (family Muridae), a gerbil, a spinymouse, and a crested rat. In some certain embodiments, a geneticallymodified mouse of the present invention is from a member of the familyMuridae. In some embodiment, a non-human animal of the present inventionis a rodent. In some certain embodiments, a rodent of the presentinvention is selected from a mouse and a rat. In some embodiments, anon-human animal of the present invention is a mouse.

In some embodiments, a non-human animal of the present invention is arodent that is a mouse of a C57BL strain selected from C57BL/A,C57BL/An, C57BL/GrFa, C57BL/KaLwN, C57BL/6, C57BL/6J, C57BL/6ByJ,C57BL/6NJ, C57BL/10, C57BL/10ScSn, C57BL/10Cr, and C57BL/Ola. In somecertain embodiments, a mouse of the present invention is a 129 strainselected from the group consisting of a strain that is 129P1, 129P2,129P3, 129X1, 129S1 (e.g., 129S1/SV, 129S1/SvIm), 129S2, 129S4, 129S5,129S9/SvEvH, 129/SvJae, 129S6 (129/SvEvTac), 129S7, 129S8, 129T1, 129T2(see, e.g., Festing et al., 1999, Mammalian Genome 10:836; Auerbach, W.et al., 2000, Biotechniques 29(5): 1024-1028, 1030, 1032). In somecertain embodiments, a genetically modified mouse of the presentinvention is a mix of an aforementioned 129 strain and an aforementionedC57BL/6 strain. In some certain embodiments, a mouse of the presentinvention is a mix of aforementioned 129 strains, or a mix ofaforementioned BL/6 strains. In some certain embodiments, a 129 strainof the mix as described herein is a 129S6 (129/SvEvTac) strain. In someembodiments, a mouse of the present invention is a BALB strain, e.g.,BALB/c strain. In some embodiments, a mouse of the present invention isa mix of a BALB strain and another aforementioned strain.

In some embodiments, a non-human animal of the present invention is arat. In some certain embodiments, a rat of the present invention isselected from a Wistar rat, an LEA strain, a Sprague Dawley strain, aFischer strain, F344, F6, and Dark Agouti. In some certain embodiments,a rat strain as described herein is a mix of two or more strainsselected from the group consisting of Wistar, LEA, Sprague Dawley,Fischer, F344, F6, and Dark Agouti.

Methods Employing Non-Human Animals Having Humanized CD274 Genes

CD274 mutant and transgenic non-human animals (e.g., mice) and cellshave been reported (Iwai, Y. et al., 2002, Proc. Nat. Acad. Sci. 99(19):12293-12297; Latchman, Y. E. et al., 2004, Proc. Nat. Acad. Sci.101(29): 10691-10696; Subudhi, S. K. et al., 2004, J. Clin. Invest.113(5):694-700; Guleria, I. et al., 2005, J. Exp. Med. 202(2):231-237;Keir, M. E. et al., 2006, J. Exp. Med. 203(4):883-895; Tanaka, K. etal., 2007, J. Immunol. 179:5204-5210; Wang, C. et al., 2008, Diabetes57:1861-1869; Wen, X. et al., 2008, Transplant. 86(11):1596-1602; Plege,A. et al., 2009, Transpl. 87(7):975-982; Cao, Y. et al., 2010, CancerRes. 71(4): 1235-1243; Plege, A. et al., 2010, Eur. Soc. OrganTransplant. 23:1293-1300; Ritprajak, P. et al., 2010, J. Immunol.184:4918-4925; Yantha, J. et al., 2010, Diabetes 59:2588-2596; Ding, Q.et al., 2011, J. Leukocyte Biol. 90:77-86; Tang, L. et al., 2011, Xi BaoYu Fen Zi Mian Yi Xue Za Zhi 27(4):357-359; Ghazizadeh, S. et al., 2012,20(1):196-203). Such mutant and transgenic animals have been useful indetermining the molecular aspects of PD-L1 expression and function, andthe role of the PD-1:PD-L1 pathway in regulating immune responses, inparticular, T cell responses. However, they have come with limitationsthat are based, in part, on the demonstrated variability in the resultsobtained. Many transgenic PD-L1 animals have employed the use oftransgenes designed to overexpress endogenous PD-L1 (see, e.g.,Ghazizadeh et al., supra), while others have focused on linkingtransgenic PD-L1 expression to tissue-specific promoters (see, e.g.,Ritprajak et al., supra). Some of these animals have displayedexpression patterns of transgenic PD-L1 that do not correlate wild-typetranscription profiles (see, e.g., Wang et al. and Yantha et al.,supra). Further, due to the use of the same source genetic material(e.g., mouse PD-L1 transgene in a mouse), PD-L1 overexpression may havecorresponded to endogenous PD-L1 rather than transgenic PD-L1 due topossible position effects of the transgene. In some cases, such animalshave demonstrated an accelerated development of disease and, therefore,raise concern that the transgene may have possibly created or modifiedone or more phenotypes, thereby complicating analysis of PD-L1 function.These results may reasonably be attributed to construct design. In thecontext of human PD-L1, pig intestinal endothelial cells engineered tostably express a CMV-driven human PD-L1 have been employed in aminiature swine skin transplantation model and provided importantinsights in ectopic human PD-L1 expression in an allograft model (Dinget al., supra). Existing PD-L1 transgenic non-human animals have proveduseful in elucidating some biological function of PD-L1 and of thePD-1:PD-L1 pathway, however, as demonstrated above, current in vivosystems exploiting PD-L1-mediated biology are incomplete. The molecularaspects of the PD-1:PD-L1 pathway and its role in the regulation ofimmune responses in the context of cancer and autoimmunity have not beenexploited in transgenic animals (e.g., mice) to its fullest potential.

Non-human animals of the present invention provide an improved in vivosystem and source of biological materials (e.g., cells) expressing human(or humanized) PD-L1 that are useful for a variety of assays. In variousembodiments, non-human animals of the present invention are used todevelop therapeutics that target PD-L1 and/or modulate PD-1:PD-L1signaling (e.g., interfering with interactions with PD-1) and/ormodulate PD-L1 interactions with other binding partners (e.g., B7-1).Such animals are particularly useful as they are fully immunocompetentin contrast to many other animal models used for in vivo studies; thus,analysis of effect of therapies is not complicated by compromised immunestatus. In various embodiments, non-human animals of the presentinvention are used to identify, screen and/or develop candidatetherapeutics (e.g., antibodies) that bind human PD-L1. In variousembodiments, non-human animals of the present invention are used toscreen and develop candidate therapeutics (e.g., antibodies) that blockinteraction of human PD-L1 with human PD-1 and/or human B7-1. In variousembodiments, non-human animals of the present invention are used todetermine the binding profile of antagonists and/or agonists of ahumanized PD-L1 polypeptide on the surface of a cell of a non-humananimal as described herein; in some embodiments, non-human animals ofthe present invention are used to determine the epitope or epitopes ofone or more candidate therapeutic antibodies that bind human PD-L1.

In various embodiments, non-human animals of the present invention areused to determine the pharmacokinetic profiles of anti-PD-L1 antibodies.In various embodiments, one or more non-human animals of the presentinvention and one or more control or reference non-human animals areeach exposed to one or more candidate therapeutic anti-PD-L1 antibodiesat various doses (e.g., 0.1 mg/kg, 0.2 mg/kg, 0.3 mg/kg, 0.4 mg/kg, 0.5mg/kg, 1 mg/kg, 2 mg/kg, 3 mg/kg, 4 mg/kg, 5 mg/mg, 7.5 mg/kg, 10 mg/kg,15 mg/kg, 20 mg/kg, 25 mg/kg, 30 mg/kg, 40 mg/kg, or 50 mg/kg or more).Candidate therapeutic antibodies may be dosed via any desired route ofadministration including parenteral and non-parenteral routes ofadministration. Parenteral routes include, e.g., intravenous,intraarterial, intraportal, intramuscular, subcutaneous,intraperitoneal, intraspinal, intrathecal, intracerebro ventricular,intracranial, intrapleural or other routes of injection. Non-parenteralroutes include, e.g., oral, nasal, transdermal, pulmonary, rectal,buccal, vaginal, ocular. Administration may also be by continuousinfusion, local administration, sustained release from implants (gels,membranes or the like), and/or intravenous injection. Blood is isolatedfrom non-human animals (humanized and control) at various time points(e.g., 0 hr, 6 hr, 1 day, 2 days, 3 days, 4 days, 5 days, 6 days, 7days, 8 days, 9 days, 10 days, 11 days, or up to 30 or more days).Various assays may be performed to determine the pharmacokineticprofiles of administered candidate therapeutic antibodies using samplesobtained from non-human animals as described herein including, but notlimited to, total IgG, anti-therapeutic antibody response,agglutination, etc.

In various embodiments, non-human animals of the present invention areused to measure the therapeutic effect of blocking or modulating PD-L1signaling (or PD-1:PD-L1 signaling, or PD-L1:B7-1 mediated interactions)and the effect on gene expression as a result of cellular changes. Invarious embodiments, a non-human animal of the present invention orcells isolated therefrom are exposed to a candidate therapeutic thatbinds a humanized PD-L1 polypeptide (or a human portion of a PD-L1polypeptide) on the surface of a cell of the non-human animal and, aftera subsequent period of time, analyzed for effects on PD-L-dependentprocesses (or interactions), for example, adhesion, apoptosis, cytokineproduction, inflammation, proliferation, self-tolerance and viralinfection (or responses).

Non-human animals of the present invention express humanized PD-L1polypeptide, thus cells, cell lines, and cell cultures can be generatedto serve as a source of humanized PD-L1 for use in binding andfunctional assays, e.g., to assay for binding or function of a PD-L1antagonist or agonist, particularly where the antagonist or agonist isspecific for a human PD-L1 sequence or epitope or, alternatively,specific for a human PD-L1 sequence or epitope that associates with PD-1and/or B7-1. In various embodiments, PD-L1 epitopes bound by candidatetherapeutic antibodies can be determined using cells isolated fromnon-human animals of the present invention.

In various embodiments, a humanized PD-L1 polypeptide expressed by anon-human animal as described herein may comprise a variant amino acidsequence. Exemplary human PD-L1 polypeptide variants include thoselisted in the SNP GeneView webpage from NCBI and are summarized in Table3. In various embodiments, non-human animals of the present inventionexpress a humanized PD-L1 polypeptide variant. In various embodiments,the variant is polymorphic at an amino acid position associated withligand binding. In various embodiments, non-human animals of the presentinvention are used to determine the effect of ligand binding throughinteraction with a polymorphic polypeptide variant of human PD-L1. Insome certain embodiments, non-human animals of the present inventionexpress a human PD-L1 polypeptide variant that appears in Table 3.

TABLE 3 Amino Chromosome mRNA Variant ID Amino Codon acid positionposition No. Allele Acid position position 5456116 111 rs111401207 A I 31 G M 3 1 5456126 121 rs139709512 C P 1 5 G A 1 5 5456128 123rs577786663 C A 3 5 T A 3 5 5456131 126 rs545701711 G V 3 6 C V 3 65462841 168 rs561746087 T Y 3 20 C Y 3 20 5462844 171 rs138119378 T N 321 C N 3 21 5462876 203 rs17718883 G R 2 32 C P 2 32 5462881 208rs140045210 T S 1 34 A T 1 34 5462893 220 rs367921713 A K 1 38 G E 1 385462919 246 rs565831052 T Y 3 46 C Y 3 46 5462929 256 rs146495642 A K 150 G E 1 50 5462931 258 rs181557130 G E 3 50 A E 3 50 5462952 279rs201730760 T D 3 57 C D 3 57 5462964 291 rs569746752 A L 3 61 G L 3 615462979 306 rs200229222 T T 3 66 C T 3 66 5462984 311 rs555485716 T I 268 C T 2 68 5462988 315 rs199878088 C N 3 69 T N 3 69 5462997 324rs41280721 C S 3 72 A R 3 72 5463108 435 rs376339401 G E 3 109 A E 3 1095465514 464 rs61752860 T L 2 119 A H 2 119 5465530 480 rs372727420 A R 3124 G R 3 124 5465594 544 rs568608390 T C 1 146 C R 1 146 5465595 545rs148141792 A H 2 146 G R 2 146 5466785 572 rs141978642 A E 2 155 T V 2155 5467847 624 rs150697452 C H 3 172 T H 3 172 5467858 635 rs369350813T M 2 176 C T 2 176 5467859 636 rs373167098 A T 3 176 G T 3 176

Cells from non-human animals of the present invention can be isolatedand used on an ad hoc basis, or can be maintained in culture for manygenerations. In various embodiments, cells from a non-human animal ofthe present invention are immortalized (e.g., via use of a virus) andmaintained in culture indefinitely (e.g., in serial cultures).

In various embodiments, cells and/or non-human animals of the presentinvention are used in various immunization regimens to determine thePD-L1-mediated functions in the immune response to an antigen (e.g., a Tcell response). In some embodiments, candidate therapeutics that bind,or block one or more functions of, human (or humanized) PD-L1 arecharacterized in a non-human animal of the present invention. Suitablemeasurements include various cellular assays, proliferation assays,serum immunoglobulin analysis (e.g., antibody titer), cytotoxicityassays, characterization of ligand-receptor interactions (e.g.,immunoprecipitation assays) and characterization of ligand-ligandinteractions. In some embodiments, non-human animals of the presentinvention are used to characterize the PD-L1-mediated functionsregulating an immune response to an antigen. In some embodiments, theantigen is associated with an autoimmune disease, disorder or condition.In some embodiments, the antigen is associated with an inflammatorydisease, disorder or condition. In some embodiments, that antigen isassociated with a neoplasm. In some embodiments, the antigen isassociated with an infectious agent (e.g., a bacterium). In someembodiments, the antigen is a test antigen (e.g., ovalbumin or OVA). Insome embodiments, the antigen is a target associated with a disease orcondition suffered by one or more human patients in need of treatment.

In various embodiments, non-human animals of the present invention areused in serum assays for determining titers of autoantibody productionfor testing the pharmaco-toxicological aspects of candidate therapeuticsthat target human PD-L1. In some embodiments, autoantibody production innon-human animals of the present invention results from one or moreautoimmune diseases, disorders or conditions induced in the non-humananimal.

In various embodiments, non-human animals of the present invention areused for challenge with one or more antigens to determine thetherapeutic potential of compounds or biological agents to modulatePD-L1-dependent regulation of an immune response, including but notlimited to, the specific T cell-dependent and B cell-dependent responsesto a given antigen.

In various embodiments, cells and/or non-human animals of the presentinvention are used in a survival and/or proliferation assay (e.g.,employing B or T cells) to screen and develop candidate therapeuticsthat modulate human PD-L1 signaling. Activation or inhibition of PD-L1plays an important role in the regulation of T cell responses, andregulation of self-tolerance by PD-L1 may result from the activation ofspecific epitopes of the extracellular domain of PD-L1, therefore,candidate PD-L1 modulators (e.g., antagonists or agonists) may beidentified, characterized and developed using cells of non-human animalsof the present invention and/or a non-human animal as described herein.In some embodiments, cells and/or non-human animals of the presentinvention are used in survival or death assay(s) to determine the effecton proliferation or apoptosis of a specific cell(s) (e.g., cancer cells)in the presence and absence of PD-L1.

In various embodiments, cells and/or non-human animals of the presentinvention are used in xenotransplantation of heterologous (e.g., human)cells or tissue to determine the PD-L1-mediated functions in thephysiological (e.g., immune) response to the transplanted human cells ortissue. In some embodiments, candidate therapeutics that bind, or blockone or more functions of, human PD-L1 are characterized in a non-humananimal of the present invention. Suitable measurements include variouscellular assays, proliferation assays, serum immunoglobulin analysis(e.g., antibody titer), cytotoxicity assays, and characterization ofligand-receptor interactions (immunoprecipitation assays). In someembodiments, non-human animals of the present invention are used tocharacterize the PD-L1-mediated functions regulating an immune responseto an antigen. In some embodiments, the antigen is associated with aneoplasm. In some embodiments, the antigen is associated with anautoimmune disease, disorder or condition. In some embodiments, theantigen is associated with an inflammatory disease, disorder orcondition. In some embodiments, the antigen is a target associated witha disease or condition suffered by one or more human patients in need oftreatment.

In various embodiments, non-human animals of the present invention areused in transplantation or adoptive transfer experiments to determinethe therapeutic potential of compounds or biological agents to modulatePD-L1-dependent regulation of xenogenic lymphocytes and their immunefunction. In various embodiments, non-human animals of the presentinvention are transplanted with human T cells; in some embodiments,naïve T cells; in some embodiments, activated T cells.

In various embodiments, cells of non-human animals of the presentinvention are used in T cell assays to determine the therapeuticpotential of compounds or biological agents to modulate PD-L1-dependentregulation of T cell-dependent response and function. Exemplary T cellassays include, but are not limited to, ELISpot, intracellular cytokinestaining, major histocompatibility complex (MHC) restriction, viralsuppression assays, cytotoxicity assays, proliferation assays andregulatory T cell suppression assays.

In various embodiments, cells of non-human animals of the presentinvention are used in cell transmigration assays to screen and developcandidate therapeutics that modulate human PD-L1. Cell transmigrationinvolves the migration of cells across the endothelium andtransmigration assays permit the measurement of interactions with, andtransmigration of, the endothelium by leukocytes or tumor cells.

In various embodiments, cells of non-human animals of the presentinvention are used in tumor cell growth (or proliferation) assays todetermine the therapeutic potential of compounds or biological agents tomodulate PD-L1-dependent regulation and/or apoptosis of tumor cells.

In various embodiments, cells of non-human animals of the presentinvention are used in cytokine production assays to determine thetherapeutic potential of compounds or biological agents to modulatePD-L1-dependent regulation of cytokine release from T cells (e.g.,interferon-γ, interleukin-10). In some embodiments, cells of non-humananimals of the present invention are used for detection (and/ormeasurement) of intracellular cytokine release resulting frominteraction of humanized PD-L1 with a drug targeting human PD-L1 or aPD-L1 binding partner (e.g., PD-1, B7-1, or a soluble version thereof).

In various embodiments, an autoimmune disease, disorder or condition isinduced in one or more non-human animals of the present invention toprovide an in vivo system for determining the therapeutic potential ofcompounds or biological agents to modulate PD-L1-dependent regulation ofone or more functions (or aspects) of the autoimmune disease, disorderor condition. Exemplary autoimmune diseases, disorders or conditionsthat may be induced in one or more non-human animals of the presentinvention include diabetes, experimental autoimmune encephalomyelitis(e.g., a model for multiple sclerosis), rheumatoid arthritis, andsystemic lupus erythematosus.

Non-human animals of the present invention provide an in vivo system forthe analysis and testing of a drug or vaccine. In various embodiments, acandidate drug or vaccine may be delivered to one or more non-humananimals of the present invention, followed by monitoring of thenon-human animals to determine one or more of the immune response to thedrug or vaccine, the safety profile of the drug or vaccine, or theeffect on a disease or condition and/or one or more symptoms of adisease or condition. In some embodiments, the vaccine targets a virussuch as, for example, human immunodeficiency virus or hepatitis virus(e.g. HCV). Exemplary methods used to determine the safety profileinclude measurements of toxicity, optimal dose concentration, efficacyof the drug or vaccine, and possible risk factors. Such drugs orvaccines may be improved and/or developed in such non-human animals.

Non-human animals of the present invention provide improved in vivosystem for elucidating mechanisms of human cell-to-cell interactionthrough adoptive transfer. In various embodiments, non-human animals ofthe present invention may by implanted with a tumor xenograft, followedby a second implantation of tumor infiltrating lymphocytes which couldbe implanted in the non-human animals by adoptive transfer to determinethe effectiveness in eradication of solid tumors or other malignancies.Such experiments may be done with human cells due to the exclusivepresence of human PD-L1 without competition with endogenous PD-L1 of thenon-human animal. Further, therapies and pharmaceuticals for use inxenotransplantation can be improved and/or developed in such non-humananimals.

Non-human animals of the present invention provide an in vivo system forassessing the pharmacokinetic properties of a drug targeting humanPD-L1. In various embodiments, a drug targeting human PD-L1 may bedelivered or administered to one or more non-human animals of thepresent invention, followed by monitoring of, or performing one or moreassays on, the non-human animals (or cells isolated therefrom) todetermine the effect of the drug on the non-human animal.Pharmacokinetic properties include, but are not limited to, how ananimal processes the drug into various metabolites (or detection of thepresence or absence of one or more drug metabolites, including, but notlimited to, toxic metabolites), drug half-life, circulating levels ofdrug after administration (e.g., serum concentration of drug), anti-drugresponse (e.g., anti-drug antibodies), drug absorption and distribution,route of administration, routes of excretion and/or clearance of thedrug. In some embodiments, pharmacokinetic and pharmacodynamicproperties of drugs (e.g., PD-L1 modulators) are monitored in or throughthe use of non-human animals of the present invention.

Non-human animals of the present invention provide an in vivo system forassessing the on-target toxicity of a drug targeting human PD-L1. Invarious embodiments, a drug targeting human PD-L1 may be delivered oradministered to one or more non-human animals of the present invention,followed by monitoring of or performing one or more assays on thenon-human animals (or cells isolated therefrom) to determine theon-target toxic effect of the drug on the non-human animal. Typically,drugs are intended to modulate one or more functions of their targets.To give but one example, a PD-L1 modulator is intended to modulatePD-L1-mediated functions (e.g., PD-L1 signaling and/or PD-L1interactions) through interacting in some way with the PD-L1 molecule onthe surface of one or more cells and, in some embodiments, blockinginteractions with one or more PD-L1 binding partners. In someembodiments, such a modulator may have an adverse effect that is anexaggeration of the desired pharmacologic action(s) of the modulator.Such effects are termed on-target effects. Exemplary on-target effectsinclude too high of a dose, chronic activation/inactivation, and correctaction in an incorrect tissue. In some embodiments, on-target effects ofa drug targeting PD-L1 identified in or through the use of non-humananimals of the present invention are used to determine a previouslyunknown function(s) of PD-L1.

Non-human animals of the present invention provide an in vivo system forassessing the off-target toxicity of a drug targeting human PD-L1. Invarious embodiments, a drug targeting human PD-L1 may be delivered oradministered to one or more non-human animals of the present invention,followed by monitoring of or performing one or more assays on thenon-human animals (or cells isolated therefrom) to determine theoff-target toxic effect of the drug on the non-human animal. Off-targeteffects can occur when a drug interacts with an unintended target (e.g.,cross-reactivity to a common epitope). Such interactions can occur in anintended or unintended tissue. To give but one example, mirror imageisomers (enantiomers) of a drug can lead to off-target toxic effects.Further, a drug can inappropriately interact with and unintentionallyactivate different receptor subtypes. Exemplary off-target effectsinclude incorrect activation/inhibition of an incorrect targetregardless of the tissue in which the incorrect target is found. In someembodiments, off-target effects of a drug targeting human PD-L1 aredetermined by comparing the effects of administering the drug tonon-human animals of the present invention to one or more referencenon-human animals.

In some embodiments, performing an assay includes determining the effecton the phenotype and/or genotype of the non-human animal to which thedrug is administered. In some embodiments, performing an assay includesdetermining lot-to-lot variability for a PD-L1 modulator (e.g., anantagonist or an agonist) or a drug targeting PD-L1. In someembodiments, performing an assay includes determining the differencesbetween the effects of a drug targeting PD-L1 administered to anon-human animal of the present invention and a reference non-humananimal. In various embodiments, reference non-human animals may have amodification as described herein, a modification that is different asdescribed herein (e.g., one that has a altered, disrupted, deleted,inserted, modified, etc. or otherwise non-functional CD274 gene) or nomodification (i.e., a wild-type non-human animal).

Exemplary parameters that may be measured in non-human animals (or inand/or using cells isolated therefrom) for assessing the pharmacokineticproperties, on-target toxicity, and/or off-target toxicity of a drugtargeting human PD-L1 include, but are not limited to, agglutination,autophagy, cell division, cell death, complement-mediated hemolysis, DNAintegrity, drug-specific antibody titer, drug metabolism, geneexpression arrays, metabolic activity, mitochondrial activity, oxidativestress, phagocytosis, protein biosynthesis, protein degradation, proteinsecretion, stress response, target tissue drug concentration, non-targettissue drug concentration, transcriptional activity and the like. Invarious embodiments, non-human animals of the present invention are usedto determine a pharmaceutically effective dose of a PD-L1 modulator(e.g., a drug targeting PD-L1).

Non-human animals of the present invention provide an improved in vivosystem for development and characterization of candidate therapeuticsfor use in cancer. In various embodiments, non-human animals of thepresent invention may be implanted with a tumor (or tumor cells),followed by administration of one or more candidate therapeutics. Insome embodiments, candidate therapeutics may include a multi-specificantibody (e.g., a bi-specific antibody) or an antibody cocktail, in someembodiments, candidate therapeutics include combination therapy such as,for example, administration of two or more mono-specific antibodiesdosed sequentially or simultaneously. The tumor may be allowedsufficient time to be established in one or more locations within thenon-human animal prior to administration of one or more candidatetherapeutics. Tumor cell proliferation, growth, survival, etc. may bemeasured both before and after administration with the candidatetherapeutic(s). Cytoxicity of candidate therapeutics may also bemeasured in the non-human animal as desired.

Non-human animals of the present invention provide an improved in vivosystem for development and characterization of candidate therapeuticsfor use in infectious diseases. In various embodiments, non-humananimals of the present invention may be infected by injection with avirus (e.g., MHV, HIV, HCV, etc.) or pathogen (e.g., bacteria), followedby administration of one or more candidate therapeutics. In someembodiments, candidate therapeutics may include a multi-specificantibody (e.g., a bi-specific antibody) or an antibody cocktail; in someembodiments, candidate therapeutics include combination therapy such as,for example, administration of two or more mono-specific antibodiesdosed sequentially or simultaneously; in some embodiments, candidatetherapeutics may include a vaccine. The virus or pathogen may be allowedsufficient time to be established in one or more locations or cellswithin the non-human animal so that one or more symptoms associated withinfection of the virus or pathogen develop in the non-human animal. Tcell proliferation and growth may be measured both before and afteradministration with the candidate therapeutic(s). Further, survival,serum and/or intracellular cytokine analysis, liver and/or spleenhistopathology may be measured in non-human animals infected with thevirus or pathogen. In some embodiments, non-human animals of the presentinvention are used to determine the extent of organ damage associatedwith viral infection. In some embodiments, non-human animals of thepresent invention are used to determine the cytokine expression profileand/or gene expression profile in various organs of non-human animalsinfected with a particular virus.

Non-human animals of the present invention can be employed to assess theefficacy of a therapeutic drug targeting human cells. In variousembodiments, one or more non-human animals of the present invention istransplanted with human cells, and a drug candidate targeting such humancells is administered to such non-human animal. The therapeutic efficacyof the drug is then determined by monitoring the human cells in thenon-human animal after the administration of the drug. Drugs that can betested in the non-human animals include both small molecule compounds,i.e., compounds of molecular weights of less than 1500 kD, 1200 kD, 1000kD, or 800 daltons, and large molecular compounds (such as proteins,e.g., antibodies), which have intended therapeutic effects for thetreatment of human diseases and conditions by targeting (e.g., bindingto and/or acting on) human cells.

In some embodiments, the drug is an anti-cancer drug, and the humancells are cancer cells, which can be cells of a primary cancer or cellsof cell lines established from a primary cancer. In some embodiments, anon-human animal of the present invention is transplanted with humancancer cells, and an anti-cancer drug is given to the non-human animal.Drug efficacy can be determined by assessing whether growth ormetastasis of the human cancer cells in the non-human animal isinhibited as a result of the administration of the drug.

In specific embodiments, the anti-cancer drug is an antibody molecule,which binds an antigen on human cancer cells. In particular embodiments,the anti-cancer drug is a bi-specific antibody that binds to an antigenon human cancer cells, and to an antigen on other human cells, forexample, cells of the human immune system (or “human immune cells”) suchas B cells and T cells.

EXAMPLES

The following examples are provided so as to describe to those ofordinary skill in the art how to make and use methods and compositionsof the invention, and are not intended to limit the scope of what theinventors regard as their invention. Unless indicated otherwise,temperature is indicated in Celsius, and pressure is at or nearatmospheric.

Example 1. Humanization of an Endogenous Cluster of Differentiation 274(CD274) Gene

This example illustrates exemplary methods of humanizing an endogenousCD274 gene encoding Programmed cell death-ligand 1 (PD-L1) in anon-human animal such as a rodent (e.g., a mouse). The methods describedin this example can be employed to humanize an endogenous CD274 gene ofa non-human animal using any human sequence, or combination of sequences(or sequence fragments) as desired. In this example, an ˜8,444 bp humanDNA fragment containing exon 3, 4 and 5 (in part) of a human CD274 genethat appears in Genbank accession NM_014143.3 (SEQ ID NO:11) is employedfor humanizing an endogenous Cd274 gene of a mouse. A targeting vectorfor humanization of the genetic material encoding the extracellulardomain, which includes an N-terminal IgV domain and an IgC2-type domain,of an endogenous Cd274 gene was constructed using VELOCIGENE® technology(see, e.g., U.S. Pat. No. 6,586,251 and Valenzuela et al., 2003, NatureBiotech. 21(6):652-659; herein incorporated by reference).

Briefly, mouse bacterial artificial chromosome (BAC) clone RP23-467A9(Invitrogen) was modified to delete the coding sequences of exons 3, 4and 5 (in part) of an endogenous mouse Cd274 gene (˜8942 bp) and insertexons 3, 4 and 5 (in part) of a human CD274 gene using an ˜8444 bp humanDNA fragment, which encodes amino acids 19-238 of a human PD-L1polypeptide. Endogenous DNA containing exon 1, exon 2, exon 6 and exon 7as well as the untranslated regions (UTRs) were retained. Sequenceanalysis of the ˜8,444 bp human DNA fragment confirmed that all humanCD274 exons (i.e., exons 3, 4 and 5 in part) and splicing signals.Sequence analysis revealed that the sequence matched the human CD274transcript NM014143.3. First, the ˜8,444 bp human DNA fragment wasamplified in two portions (FIG. 2, top). A 5′ portion (˜4,494 bp)containing a human CD274 exon 2 and part of intron 3 was amplified byPCR using a 3′ primer that contained an NheI restriction site and a 5′primer containing a mouse homology box to facilitate bacterialhomologous recombination. A 3′ portion (˜3,950 bp) containing part ofintron 3, exon 4, intron 4 and part of exon 5 (˜32 bp) was amplified byPCR using a 5′ primer that contained an XhoI restriction site and a 3′primer containing a mouse homology box to facilitate bacterialhomologous recombination. The PCR products were gel purified andseparately digested with the corresponding restriction endonucleases.The NheI-XhoI restriction sites were employed to ligate the ˜4,494 bpand ˜3,950 bp DNA fragments to the 5′ and 3′ ends of a ˜4,996 bpself-deleting neomycin cassette (loxP-hUb1-em7-Neo-pA-mPrm1-Crei-loxP;see U.S. Pat. Nos. 8,697,851, 8,518,392 and 8,354,389, all of which arehereby incorporated by reference) in reverse orientation to the DNAfragments containing human CD274 coding sequence. Subsequent selectionemployed neomycin. By design, the junction between the portion of humanCD274 exon 5 (i.e., initial 32 bp) and endogenous Cd274 exon 5 preservedthe open reading frame in exon 5 (FIG. 2) and created a unique CD274exon 5 (AACTACCTCTGGCACATCCTCCAAATGAAA GGACTCACTG GGTGCTTCTG GGATCCATCCTGTTGTTCCT CATTGTAGTG TCCACGGTCC TCCTCTTCTT GAGAAAACAA G; SEQ ID NO:12).The resulting targeting vector contained, from 5′ to 3′, a 5′ homologyarm containing ˜92.9 kb of mouse genomic DNA from BAC clone RP23-467A9,a ˜4,494 bp human DNA fragment containing exon 3 and part of intron 3 ofa human CD274 gene, a self-deleting neomycin cassette flanked by loxPsites, a ˜3950 bp human DNA fragment containing part of intron 3, exon4, intron 4 and the first 32 bp of exon 5 of a human CD274 gene, and˜67.6 kb of mouse genomic DNA from BAC clone RP23-467A9.

The modified RP23-467A9 clone described above was used to electroporatemouse embryonic stem (ES) cells to create modified ES cells comprisingan endogenous CD274 gene that is humanized from exon 3 through to partof exon 5 (i.e., a deletion of ˜8,964 of the endogenous Cd274 gene andinsertion of ˜8,444 bp of human CD274 sequence). Positively targeted EScells containing a humanized CD274 gene were identified by an assay(Valenzuela et al., supra) that detected the presence of human CD274sequences (e.g., exon 3, 4 and part of exon 5) and confirmed thedeletion and/or retention of mouse Cd274 sequences (e.g., exon 3, 4 andpart of 5 and/or exon 1, 2, 6 and 7). Table 4 sets forth exemplarysequences of primers and probes that were used to confirm humanizationof an endogenous mouse Cd274 gene as described above (illustrated inFIG. 3).

Nucleotide sequences across various junctions are depicted in thediagrams in FIG. 2. The nucleotide sequence across the upstreaminsertion point included the following, which indicates endogenous mouseCd274 sequence (contained within the parentheses below) contiguous withhuman CD274 sequence downstream of the insertion

(SEQ ID NO: 13) (TAACCTTTTA CCCAGGTTTT CAGATGTGTT TGGAGGAGTTTTCTGTCTTC TGAGGGCTGG TCCTCTTTCCT TTTCAGCGTTTACT) GTCAGGTTCC CAAGGACCTA TATGTGGTAG AGTATGGTAGCAATATGACA ATTGAATGCA AATTCCCAGTAGAA.

(SEQ ID NO: 14) TTTGTATTAA CTCTCTGTGA AGAAATTACC TCACAAATCTATTGCTGTC (GCTAGCTCGCTACCTT AGGACCGTTATAGTTACTAGC C ATAACTTCGTATAGCATACATTATACGAAGTTATTCCAGACATG ATAAGATACA TTGATGAGTT TGGACAAACCACAACTAGAA TGCAGTGAAA AAAATGCTTT ATTTGTGAAATTTGTGATGC TATTGCTTTA TTTGTAACCA TTATAAGCTG).

The nucleotide sequence across the 3′ end of the self-deleting Neomycincassette included the following, which indicates cassette sequence(contained within the parentheses below with loxP sequence in bold fontand an XhoI restriction site italicized) contiguous with human CD274sequence downstream of the insertion point:

(SEQ ID NO: 15) (GTGAGGAGGG GGGCGCCCGC GGGAGGCGCC AAAACCCGGCGCGGAGGCCA TGCAT ATAACTTCGT ATAGCATACA TTATACGAAG TTATCTCGAG) CTTGGTAAAG GAATGGAGAA TTAAGGCTCTAGATCATTAG TGGTTACACT ATAGTATTAG AAGTAAAAAAAAGATTATAC CAACAAAATA AGAACATGTT AATGTACTTGTAATGAATAA ACATGAATAA AGCTCTTATG CTATA.

The nucleotide sequence across the 3′ end of the human CD274 sequenceincluded the following, which indicates human CD274 sequence contiguouswith mouse Cd274 sequence (contained within the parentheses below):

(SEQ ID NO: 16) TTTATCTTTA GTCAGTTTGT TTTCGTTTTGT TTTGTTTTTCAGAACTACCT CTGGCACATC CTCCAAATGA AAGG (ACTCACTGGGTGCTTCTGGG ATCCATCCTG TTGTTCCTCA TTGTAGTGTCCACGGTCCTC CTCTTCTTGA GAAAACAAGG TATTTCCTCCATTG.

The nucleotide sequence across the insertion point after deletion of theneomycin cassette included the following, which indicates human genomicsequence juxtaposed with remaining cassette sequence loxP sequence(contained within the parentheses below with NheI and XhoI restrictionsites italicized and loxP sequence in bold font):

(SEQ ID NO: 17) TCCTAGCCG TTTGTATTA ACTCTCTGTG AAGAAATTACCTCACAAATCT ATTGCTGTC (GCTAGCTCGCTACCTT AGGACCGTTATAGTTACTAGCATAACTTCGT ATAGCATACATTATACGAAGTTAT CTCGAG)CTTGGTAAAGGAATGGAGAATTAAGGCTCTAGATCATTAGTGGTTACACTATAGTATTAGAAGTAAAAAAAAGATTATACCAACAAAATAAGAA.

Positive ES cell clones were then used to implant female mice using theVELOCIMOUSE® method (see, e.g., U.S. Pat. No. 7,294,754 and Poueymirouet al., 2007, Nature Biotech. 25(1):91-99) to generate a litter of pupscontaining an insertion of human CD274 exon 3, 4 and part of human CD274exon 5 into an endogenous mouse Cd274 gene. Mice bearing thehumanization of exon 3, 4 and 5 in part (i.e., the ˜8,444 bp human DNAfragment) of an endogenous Cd274 gene were again confirmed andidentified by genotyping of DNA isolated from tail snips using an assay(Valenzuela et al., supra) that detected the presence of the human CD274gene sequences. Pups are genotyped and cohorts of animals heterozygousfor the humanized Pdcd1 gene construct are selected forcharacterization. Mice are also bred to homozygosity.

TABLE 4 Name Description Sequence (5′-3′) 7096 hTU Forward primerCCGGCTGTTGAAGGACCAG SEQ ID NO: 18 Probe TCTCCCTGGGAAATGCTGCACTTCAGSEQ ID NO: 19 Reverse primer TGCATCCTGCAATTTCACATCTG SEQ ID NO: 207096 hTD Forward primer ACACAGGTATCTCGCCATTCC SEQ ID NO: 21 ProbeAGCCACTCAAACTTTGGCATT SEQ ID NO: 22 Reverse primerGGTCATCCTTGAAGTTTAGTTTAGC SEQ ID NO: 23 7096 TU Forward primerCAGGACGCAGGCGTTTAC SEQ ID NO: 24 Probe CTGCATAATCAGCTACGGTGGTGCGGSEQ ID NO: 25 Reverse primer TTCAGCGTGATTCGCTTGTAG SEQ ID NO: 26 7096 TDForward primer CTGGAGTGCCCAAGAGTC SEQ ID NO: 27 ProbeCAGACATGGAAGAAACACAACCCGCAC SEQ ID NO: 28 Reverse primerCTGCTAAGCCGCTTCTGTC SEQ ID NO: 29

Example 2. Expression of Humanized PD-L1 on Activated T Cells

This Example demonstrates that non-human animals (e.g., rodents)modified to contain a humanized CD274 gene according to Example 1express a humanized PD-L1 polypeptide on the surface of activatedlymphocytes. In this Example, activated T cells from wild-type mice andmice whose genome contained a humanized CD274 gene as described inExample 1 were stained with commercial anti-PD-L1 antibodies todetermine the expression of PD-L1 in stimulated and unstimulated Tcells.

Briefly, spleens were harvested and processed from a wild-type mouse anda mouse homozygous for an endogenous CD274 gene as described in Example1 into single cell suspensions by mechanical dissociation. Cells werewashed in media (RPMI supplemented with 10% FBS) and re-suspended at1×10⁶/mL and 200 PL (200,000 cells) were plated in 96-well plates. Cellsin selected wells were stimulated with anti-CD3 and anti-CD28 antibodies(both at 1 μg/mL) for 72 hours. Cells were stained for FACS according tomanufacturer's specifications with antibodies recognizing CD3, CD4, CD8and human (clone MIH1, BD Biosciences) or mouse (clone 10F.9G2,eBioscience) PD-L1. Stained cells were run on LSRII flow cytometer anddata was analyzed using FLOWJO™ software. CD8⁺ T (CD3⁺CD8⁺) and CD4⁺ T(CD3⁺CD4⁺) cells were gated and analyzed for expression of human andmouse PD-L1. Exemplary mean fluorescence intensity values are set forthin Table 5.

As shown in Table 5, mice bearing a humanized CD274 gene as described inExample 1 express a PD-L1 polypeptide that comprises a human portion andan endogenous portion on activated T cells. The human portion isdetectably expressed via recognition by an antibody that is reactive toa fully human PD-L1 polypeptide, which antibody does not recognize amouse PD-L1 polypeptide in wild-type mice. In contrast, the anti-mousePD-L antibody clone 10F.9G2 demonstrated a high level of staining formouse PD-L1 in wild-type mice after anti-CD3/anti-CD28 stimulation, anda marginal level of staining in humanized PD-L1 mice. This is mostlikely due to partial cross-reactivity to human PD-L1.

TABLE 5 Mean Fluorescence Intensity CD8⁺ T cells CD4⁺ T cells α-hPD-α-mPD- α-hPD- α-mPD- Genotype Sample L1 L1 L1 L1 humanized Isotype 78 84−55 −52 CD274 control Unstimulated 271 160 114 61 Stimulated 384 276 457155 wild- Isotype 64 64 −58 −39 type control Unstimulated 62 712 −45 538Stimulated 113 3174 22 2805 α-hPD-L1: anti-human PD-L1 α-mPD-L1:anti-mouse PD-L1

Example 3. In Vivo Efficacy of PD-L1 Modulators

This Example demonstrates that non-human animals (e.g., rodents)modified to contain a humanized CD274 gene according to Example 1 can beused in an in vivo assay to screen PD-L1 modulators (e.g., anti-PD-L1antibodies) and determine various characteristics such as, for example,reducing tumor growth and/or killing of tumor cells. In this Example,several anti-PD-L1 antibodies are screened in mice homozygous forhumanization of an endogenous CD274 gene (as described in Example 1)subcutaneously injected with MC38.ova tumor cells to determine theoptimal antibody dose that promotes tumor regression and the extent towhich anti-PD-L1 antibodies mediate killing of tumor cells.

Briefly, mice were divided evenly according to body weight into fivetreatment or control groups for Study 1 (n=5 to 8 mice per group) orrandomized into seven treatment groups for Study 2 (n=5 to 6 mice).Study 1 animals were anesthetized by isoflurane inhalation and theninjected subcutaneously into the right flank with 1×10⁶ MC38.ova cellsin suspension of 100 μL of DMEM (day 0). MC38.Ova (mouse colonadenocarcinoma) cells were engineered to express chicken ovalbumin inorder to increase tumor immunogenicity and to allow monitoring of theT-cell immune responses to well-defined antigenic ovalbumin peptides.MC38.ova cells were also transduced with a lentiviral vector expressingfull-length human PD-L1 under control of an SFFV viral promoter, andsorted for positive expression of human PD-L1 (MC38.ova/hPD-L1) by flowcytometry using an antibody specific for human PD-L1 (clone MIH1, BDBiosciences). MC38.ova cells also express a low level of endogenousmouse PD-L1. Study 1 treatment groups were intraperitoneally injectedwith 500 μg of either one of three anti-PD-L1 antibodies or one of twoisotype control antibodies not specific for PD-L1 on days 3, 7, 10, 14,and 17. A single group of animals was left untreated. Study 2 animalswere also subcutaneously implanted with 1×10⁶ MC38.Ova/hPD-L1 cells (day0), however, study 2 treatment groups were intraperitoneallyadministered with an anti-PD-L1 antibody (Ab A, Ab B, or Ab C) orcontrol antibodies (i.e., not specific for PD-L1) at doses of 10 mg/kgor 5 mg/kg. Treatment groups were administered antibody on days 3, 7,10, 14, and 17. Experimental dosing and treatment protocol for eachstudy is set forth in Table 6.

TABLE 6 Study 1 Study 2 Antibody Dose (μg) Antibody Dose (mg/kg) Ab A500 Ab A 10 Ab B 500 Ab A 5 Ab C 500 Ab B 10 Control 1 500 Ab B 5Control 2 500 Ab C 10 Ab C 5 Control 1 10

For each study, tumor volumes were monitored by caliper measurementtwice per week for the duration of the experiment (17 days for Study 1,21 days for Study 2) and percent survival was recorded at the end ofeach study. The number of tumor-free mice was also scored at the end ofeach study. Exemplary results, expressed as mean tumor volume (mm³±SD),percent survival, and number of tumor-free mice, are set forth in Tables7 and 8. Exemplary tumor growth curves are provided in FIG. 4.

TABLE 7 Study 1 Mean tumor volume Tumor- (mm³ ± SD) Survival (%) freemice Antibody Days 10 Day 17 Day 10 Day 17 Day 17 Ab A  6 ± 10 2 ± 5 100100 4/5 Ab B 16 ± 17 0 ± 0 100 100 5/5 Ab C 13 ± 14 0 ± 0 100 100 5/5Control 1 65 ± 27 148 ± 109 100 100 0/5 Control 2 54 ± 44 80 ± 63 100100 0/5

TABLE 8 Study 2 Mean tumor volume (mm³ ± SD) Survival (%)Tumor-free-mice Day 10 Day 21 Day 10 Day 21 Day 21 10 5 10 5 10 5 10 510 5 Antibody mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kgmg/kg Ab A 14 ± 15 17 ± 4  19 ± 922 108 ± 101 100 100 100 100 3/6 2/5 AbB 18 ± 10 23 ± 10  34 ± 81  231 ± 238 100 100 100 100 5/6 1/5 Ab C 10 ±8  25 ± 929  7 ± 16   37 ± 59  100 100 100 100 5/6 3/5 Control 1 55 ± 37N/A 534 ± 356 N/A 100 N/A 100 N/A 0/6 N/A

For Study 1, all three anti-PD-L1 antibodies were efficacious inpromoting tumor regression at 500 μg/mouse with all mice from treatmentgroups that received Ab B and Ab C being tumor free at day 17 (Table 7).In the Ab A treatment group, four of five mice (80%) were tumor free byday 17, whereas none of the animals in the control groups weretumor-free. One-way ANOVA with Dunnett's multiple comparison post-testrevealed a significant difference in tumor volumes between treatmentswith anti-PD-L1 antibodies and the control antibodies with a p value<0.05. Control 2 is an unrelated matched isotype control antibody, whilecontrol 1 is an unrelated unmatched isotype control antibody.

For Study 2, administration of the selected anti-PD-L1 antibodiesresulted in inhibition of tumor growth and thereby promoted tumorregression (Table 8). All anti-PD-L1 antibodies tested were efficaciousat 10 mg/kg and 5 mg/kg, and promoted tumor regression in treated micein a dose dependent manner throughout the course of the experiment. Noneof the animals treated with control antibodies were tumor-free (Table8). One-way ANOVA with Tukey's multiple comparison post-test revealed asignificant difference in tumor volumes between treatments with theanti-PD-L1 antibodies and control antibodies with p value <0.05 orlower. Control 1 is an unrelated matched isotype control.

As shown in FIG. 4 and Tables 7 and 8, anti-PD-L1 antibodiessignificantly inhibited tumor growth in a prophylactic MC38.ova/hPD-L1tumor growth model in mice having a humanized CD274 gene as described inExample 1. Anti-PD-L1 antibody therapy at 10 mg/kg and 5 mg/kg promotedtumor regression in all mice throughout the course of the experimentresulting in three out of six mice remaining tumor-free in 10 mg/kggroup and two out of five mice remaining tumor-free in 5 mg/kg treatmentgroup by Day 21, whereas none of the animals remained tumor-free in thecontrol group (0/6) (FIG. 4). One-way ANOVA with Dunnett's multiplecomparison post-test revealed a significant difference in tumor volumeson Day 21 between anti-PD-L1 and control antibody treatments with a pvalue <0.01 (5 mg/kg treatment group) and p value <0.0001 (10 mg/kgtreatment group).

In a similar experiment, intact functional PD-L1 signaling in micecontaining a humanized CD274 gene as described in Example 1 wasinvestigated by measuring CD8⁺ and CD3⁺ T cell responses in splenocytesof tumor-bearing mice treated with anti-PD-L1 antibody.

Briefly, splenocytes were isolated from mice containing a humanizedCD274 gene as described in Example 1 treated with anti-PD-L1 or controlantibody at the end of the experiment on Day 21 (described above). TotalRNA was isolated, and real-time PCR was performed on reverse transcribedcDNA using oligonucleotides and TAQMAN™ probe mix specific for mouseCD8b, mouse CD3ζ (Mm00446171_m1, Applied Biosystems), human PD-L1 andmouse PD-L1 (Table 9). Samples were normalized relative to expression ofmouse cyclophilin B. Exemplary results are provided in FIG. 5.

TABLE 9 Name Description Sequence (5′-3′) mCD8b ForwardGCTCTGGCTGGTCTTCAG SEQ ID NO: 30 primer TATG Probe AGCAGCTCTG CCCTCATSEQ ID NO: 31 Reverse TTGCCGTATGGTTGGTTT SEQ ID NO: 32 primer GAAChPD-L1 Forward ACAGCCTGCTGTCACTTG SEQ ID NO: 33 primer C ProbeTACGGGCGTTTACTGTCA SEQ ID NO: 34 C Reverse ACCACATATAGGTCCTTGSEQ ID NO: 35 primer GGAAC mPD-L1 Forward TTCTCAATGTGACCAGCASEQ ID NO: 36 primer GTC Probe AGGGTCAACGCCACAGCG SEQ ID NO: 37 AATGAReverse TCCTGTTCTGTGGAGGAT SEQ ID NO: 38 primer GTG

As shown in FIG. 5, administration of anti-hPD-L1 antibody induced anincrease in the number of CD8⁺ and CD3⁺ T cells in splenocytes of micecontaining a humanized CD274 gene (as described in Example 1) andbearing MC38.ova/hPD-L1 tumors. This confirms that mice containing ahumanized CD274 gene (as described in Example 1) demonstrate properexpression and signaling through humanized PD-L1 on the cell surface inthat PD-L1 expression by MC38.ova cells was not able to suppressproliferation of anti-tumor CD8⁺ T cells. Overall, the demonstratedincrease in T cells as compared to control-treated mice was observed forboth treatment groups, however, statistical difference in CD8b (p value<0.01) and CD3 (p<0.001) levels using a one-way ANOVA with Dunnett'smultiple comparison post-test was only reached between the 10 mg/kganti-PD-L1 antibody and control treatment groups.

Human PD-L1 mRNA expression was measured with human specific probesdesigned for the extracellular portion of human PD-L1 polypeptide (Table9) and confirmed proper expression of humanized PD-L1 protein on thecell surface (FIG. 5). Additionally, measurement of mouse PD-L1 mRNAexpression with primers designed to detect the extracellular portion ofmouse PD-L1 (Table 9) failed to produce a product. These data confirmthe flow cytometry results presented in Table 5, i.e., humanized PD-L1mice indeed express humanized PD-L1 that is intact and functional on thecell surface.

Taken together, this example demonstrates that non-human animals of thepresent invention can be used to assess the in vivo efficacy of drugs(e.g., antibodies) that target PD-L1, and such animals are useful indiscriminating the therapeutic effect of anti-PD-L1 antibodies.Moreover, non-human animals described herein can be used to assess theextent to which drugs targeting PD-L1 can promote the regression oftumors and/or mediate killing of tumor cells. Non-human animals (e.g.mice) of the present invention demonstrate expression of functionalhumanized PD-L1 polypeptide on the cell surface and proper PD-L1regulation of immune responses via inhibition of PD-L1-dependentsuppression of CD8⁺ T cells in a tumor model.

EQUIVALENTS

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated by those skilled in the art thatvarious alterations, modifications, and improvements will readily occurto those skilled in the art. Such alterations, modifications, andimprovements are intended to be part of this disclosure, and areintended to be within the spirit and scope of the invention.Accordingly, the foregoing description and drawing are by way of exampleonly and the invention is described in detail by the claims that follow.

Use of ordinal terms such as “first,” “second,” “third,” etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

The articles “a” and “an” as used herein in the specification and in theclaims, unless clearly indicated to the contrary, should be understoodto include the plural referents. Claims or descriptions that include“or” between one or more members of a group are considered satisfied ifone, more than one, or all of the group members are present in, employedin, or otherwise relevant to a given product or process unless indicatedto the contrary or otherwise evident from the context. The inventionincludes embodiments in which exactly one member of the group is presentin, employed in, or otherwise relevant to a given product or process.The invention also includes embodiments in which more than one, or theentire group members are present in, employed in, or otherwise relevantto a given product or process. Furthermore, it is to be understood thatthe invention encompasses all variations, combinations, and permutationsin which one or more limitations, elements, clauses, descriptive terms,etc., from one or more of the listed claims is introduced into anotherclaim dependent on the same base claim (or, as relevant, any otherclaim) unless otherwise indicated or unless it would be evident to oneof ordinary skill in the art that a contradiction or inconsistency wouldarise. Where elements are presented as lists, (e.g., in Markush group orsimilar format) it is to be understood that each subgroup of theelements is also disclosed, and any element(s) can be removed from thegroup. It should be understood that, in general, where the invention, oraspects of the invention, is/are referred to as comprising particularelements, features, etc., certain embodiments of the invention oraspects of the invention consist, or consist essentially of, suchelements, features, etc. For purposes of simplicity those embodimentshave not in every case been specifically set forth in so many wordsherein. It should also be understood that any embodiment or aspect ofthe invention can be explicitly excluded from the claims, regardless ofwhether the specific exclusion is recited in the specification.

Those skilled in the art will appreciate typical standards of deviationor error attributable to values obtained in assays or other processesdescribed herein. The publications, websites and other referencematerials referenced herein to describe the background of the inventionand to provide additional detail regarding its practice are herebyincorporated by reference.

We claim:
 1. A genetically modified mouse whose genome comprises areplacement of a genomic fragment of an endogenous mouse CD274 gene atan endogenous mouse CD274 locus with a human CD274 nucleic acid sequenceto form a humanized CD274 gene, wherein the genomic fragment of theendogenous mouse CD274 gene being replaced encodes the extracellularsequence of the endogenous mouse CD274 polypeptide, and the human CD274nucleic acid sequence encodes the extracellular sequence of a humanCD274 polypeptide; wherein the humanized CD274 gene comprises the humanCD274 nucleic acid sequence which is operably linked to (i) a nucleicacid sequence encoding the intracellular and transmembrane sequences ofthe endogenous mouse CD274 polypeptide; and (ii) the endogenous mouseCD274 promoter at the endogenous mouse CD274 locus; and wherein themouse expresses from the humanized CD274 gene, a functional humanizedCD274 polypeptide comprising the extracellular sequence of the humanCD274 polypeptide, and the intracellular and transmembrane sequences ofthe endogenous mouse CD274 polypeptide.
 2. The genetically modifiedmouse of claim 1, wherein the humanized CD274 gene comprises (i) exon 1and exon 2 of the endogenous mouse CD274 gene, (ii) exon 3, exon 4, anda portion of exon 5 of the human CD274 gene, and (iii) exon 6, exon 7,and a portion of exon 5 of the endogenous mouse CD274 gene.
 3. A methodof screening for a drug capable of treating a tumor, the methodcomprising the steps of (a) administering tumor cells to the mouse ofclaim 1 such that a tumor is formed in the mouse, (b) administering adrug to the mouse of step (a); and (c) determining whether tumor growthis reduced in the mouse of step (b), wherein a drug that reduces tumorgrowth is capable of treating a tumor.
 4. The method of claim 3, whereinthe drug is an antibody directed against human CD274.
 5. The mouse ofclaim 1, wherein the human CD274 nucleic acid sequence encodes aminoacids 19-238 of the human CD274 polypeptide.
 6. A method of making agenetically modified mouse, comprising (a) inserting a nucleic acidsequence that encodes the extracellular sequence of a human CD274polypeptide into an endogenous mouse CD274 gene in an isolated mouseembryonic stem cell, wherein the nucleic acid sequence replaces agenomic fragment of the endogenous mouse CD274 gene which fragmentencodes the extracellular sequence of the endogenous mouse CD274polypeptide, thereby forming a humanized CD274 gene, wherein thehumanized CD274 gene comprises the nucleic acid sequence encoding theextracellular sequence of the human CD274 polypeptide, operably linkedto (i) a nucleic acid sequence encoding the intracellular sequence andthe transmembrane sequence of an endogenous mouse CD274 polypeptide, and(ii) the endogenous mouse CD274 promoter at the endogenous mouse CD274locus; and (b) obtaining a mouse using the mouse embryonic stem cellobtained in step (a), wherein the genome of the mouse comprises thehumanized CD274 gene at the endogenous mouse CD274 locus; wherein themouse expresses a functional humanized CD274 polypeptide comprising theextracellular sequence of the human CD274 polypeptide, and theintracellular and transmembrane sequences of the endogenous mouse CD274polypeptide.
 7. The method of claim 6, wherein the nucleic acid sequenceencoding the extracellular sequence of the human CD274 polypeptideencodes amino acids 19-238 of the human CD274 polypeptide.
 8. The methodof claim 6, wherein the nucleic acid sequence encoding the extracellularsequence of the human CD274 polypeptide comprises exon 3, exon 4, and aportion of exon 5 of a human CD274 gene.
 9. The method of claim 8,wherein the humanized CD274 gene comprises (i) exon 1 and exon 2 of theendogenous mouse CD274 gene; (ii) exon 3, exon 4, and a portion of exon5 of a human CD274 gene; and (iii) exon 6, exon 7, and a portion of exon5 of the endogenous mouse CD274 gene.
 10. A nucleic acid vector formaking a genetically modified mouse, comprising, a nucleic acid sequenceencoding the extracellular sequence of a human CD274 polypeptide andcomprising exon 3, exon 4, and a portion of exon 5 of a human CD274gene, wherein the nucleic acid sequence is operably linked to (i) anucleic acid sequence encoding the intracellular sequence and thetransmembrane sequence of a mouse CD274 polypeptide, and (ii) a mouseCD274 promoter; wherein the vector is capable of integrating into amouse CD274 locus and expressing a functional humanized CD274polypeptide which comprises the extracellular sequence of the humanCD274 polypeptide, and the intracellular and transmembrane sequences ofthe mouse CD274 polypeptide.